diff --git a/frontend/src/components/AudioAnalysis.tsx b/frontend/src/components/AudioAnalysis.tsx
index cb830fa..4a8052f 100644
--- a/frontend/src/components/AudioAnalysis.tsx
+++ b/frontend/src/components/AudioAnalysis.tsx
@@ -148,7 +148,7 @@ export function AudioAnalysis({ result, analyzing, onAnalyze, showAnalyzeButton
                                 <p className="text-xs font-semibold tracking-wider text-muted-foreground uppercase">Spectrum Meta</p>
                                 <ul className="text-sm space-y-1">
                                     <li className="flex justify-between">
-                                        <span className="text-muted-foreground">Analysis Frames:</span>
+                                        <span className="text-muted-foreground">Display Frames:</span>
                                         <span className="font-medium font-mono">{frames.toLocaleString()}</span>
                                     </li>
                                     <li className="flex justify-between">
diff --git a/frontend/src/components/AudioAnalysisPage.tsx b/frontend/src/components/AudioAnalysisPage.tsx
index f907a3e..fd28169 100644
--- a/frontend/src/components/AudioAnalysisPage.tsx
+++ b/frontend/src/components/AudioAnalysisPage.tsx
@@ -1,5 +1,6 @@
 import { useState, useCallback, useRef, useEffect, type ChangeEvent, type DragEvent, type CSSProperties } from "react";
 import { Button } from "@/components/ui/button";
+import { Progress } from "@/components/ui/progress";
 import { Upload, ArrowLeft, Trash2, Download } from "lucide-react";
 import { AudioAnalysis } from "@/components/AudioAnalysis";
 import { SpectrumVisualization } from "@/components/SpectrumVisualization";
@@ -37,12 +38,14 @@ function fileNameFromPath(filePath: string): string {
 export function AudioAnalysisPage({ onBack }: AudioAnalysisPageProps) {
     const {
         analyzing,
+        analysisProgress,
         result,
         analyzeFile,
         analyzeFilePath,
         clearResult,
         selectedFilePath,
         spectrumLoading,
+        spectrumProgress,
         reAnalyzeSpectrum,
     } = useAudioAnalysis();
 
@@ -229,9 +232,14 @@ export function AudioAnalysisPage({ onBack }: AudioAnalysisPageProps) {
             )}
 
             {analyzing && !result && (
-                <div className="flex flex-col items-center justify-center py-16">
-                    <div className="animate-spin rounded-full h-12 w-12 border-b-2 border-primary mb-4"></div>
-                    <p className="text-sm text-muted-foreground">Analyzing audio file...</p>
+                <div className="flex h-[400px] items-center justify-center">
+                    <div className="w-full max-w-md space-y-2">
+                        <div className="flex items-center justify-between text-sm text-muted-foreground">
+                            <span>Processing...</span>
+                            <span className="tabular-nums">{analysisProgress.percent}%</span>
+                        </div>
+                        <Progress value={analysisProgress.percent} className="h-2 w-full" />
+                    </div>
                 </div>
             )}
 
@@ -252,6 +260,7 @@ export function AudioAnalysisPage({ onBack }: AudioAnalysisPageProps) {
                         fileName={fileName}
                         onReAnalyze={reAnalyzeSpectrum}
                         isAnalyzingSpectrum={spectrumLoading}
+                        spectrumProgress={spectrumProgress}
                     />
                 </div>
             )}
diff --git a/frontend/src/components/SpectrumVisualization.tsx b/frontend/src/components/SpectrumVisualization.tsx
index 7af73c7..bcc5b9c 100644
--- a/frontend/src/components/SpectrumVisualization.tsx
+++ b/frontend/src/components/SpectrumVisualization.tsx
@@ -1,6 +1,7 @@
 import { useEffect, useRef, useState, forwardRef, useImperativeHandle } from "react";
 import type { SpectrumData } from "@/types/api";
 import { Label } from "@/components/ui/label";
+import { Progress } from "@/components/ui/progress";
 import {
     loadAudioAnalysisPreferences,
     saveAudioAnalysisPreferences,
@@ -27,6 +28,10 @@ interface SpectrumVisualizationProps {
     fileName?: string;
     onReAnalyze?: (fftSize: number, windowFunction: string) => void;
     isAnalyzingSpectrum?: boolean;
+    spectrumProgress?: {
+        percent: number;
+        message: string;
+    };
 }
 
 type ColorScheme = AnalyzerColorScheme;
@@ -489,6 +494,7 @@ export const SpectrumVisualization = forwardRef<SpectrumVisualizationHandle, Spe
     fileName,
     onReAnalyze,
     isAnalyzingSpectrum,
+    spectrumProgress,
 }, ref) => {
     const canvasRef = useRef<HTMLCanvasElement>(null);
     const preferencesRef = useRef(loadAudioAnalysisPreferences());
@@ -565,6 +571,8 @@ export const SpectrumVisualization = forwardRef<SpectrumVisualizationHandle, Spe
         }
     };
 
+    const spectrumPercent = Math.round(Math.max(0, Math.min(100, spectrumProgress?.percent ?? 0)));
+
     return (
         <div className="space-y-4">
             <div className="flex flex-wrap items-center gap-3 sm:gap-4 p-1">
@@ -638,9 +646,14 @@ export const SpectrumVisualization = forwardRef<SpectrumVisualizationHandle, Spe
 
             <div className="relative border border-white/10 rounded-lg overflow-hidden bg-black shadow-xl">
                 {isAnalyzingSpectrum && (
-                    <div className="absolute inset-0 bg-black/60 flex flex-col items-center justify-center z-10 backdrop-blur-sm">
-                        <div className="animate-spin rounded-full h-8 w-8 border-b-2 border-primary mb-2"></div>
-                        <p className="text-sm text-foreground">Re-analyzing spectrum...</p>
+                    <div className="absolute inset-0 z-10 grid place-items-center bg-black/60 backdrop-blur-sm">
+                        <div className="w-full max-w-xs space-y-2 px-4">
+                            <div className="flex items-center justify-between text-sm text-foreground/90">
+                                <span>Processing...</span>
+                                <span className="tabular-nums">{spectrumPercent}%</span>
+                            </div>
+                            <Progress value={spectrumPercent} className="h-2 w-full" />
+                        </div>
                     </div>
                 )}
                 <canvas
diff --git a/frontend/src/hooks/useAudioAnalysis.ts b/frontend/src/hooks/useAudioAnalysis.ts
index 8a33c50..9823be1 100644
--- a/frontend/src/hooks/useAudioAnalysis.ts
+++ b/frontend/src/hooks/useAudioAnalysis.ts
@@ -1,8 +1,13 @@
-import { useState, useCallback, useRef } from "react";
+import { useState, useCallback, useRef, useEffect, type MutableRefObject } from "react";
 import type { AnalysisResult } from "@/types/api";
 import { logger } from "@/lib/logger";
 import { toastWithSound as toast } from "@/lib/toast-with-sound";
-import { analyzeFlacArrayBuffer, analyzeFlacFile, analyzeSpectrumFromSamples } from "@/lib/flac-analysis";
+import {
+    analyzeFlacArrayBuffer,
+    analyzeFlacFile,
+    analyzeSpectrumFromSamples,
+    type AnalysisProgress,
+} from "@/lib/flac-analysis";
 import { loadAudioAnalysisPreferences } from "@/lib/audio-analysis-preferences";
 
 type WindowFunction = "hann" | "hamming" | "blackman" | "rectangular";
@@ -24,14 +29,34 @@ function fileNameFromPath(filePath: string): string {
     return parts[parts.length - 1] || filePath;
 }
 
-function base64ToArrayBuffer(base64: string): ArrayBuffer {
+function nextUiTick(): Promise<void> {
+    return new Promise((resolve) => setTimeout(resolve, 0));
+}
+
+async function base64ToArrayBuffer(base64: string, shouldCancel?: () => boolean): Promise<ArrayBuffer> {
     const clean = base64.includes(",") ? base64.split(",")[1] : base64;
-    const binary = atob(clean);
-    const len = binary.length;
-    const bytes = new Uint8Array(len);
-    for (let i = 0; i < len; i++) {
-        bytes[i] = binary.charCodeAt(i);
+    const padding = clean.endsWith("==") ? 2 : clean.endsWith("=") ? 1 : 0;
+    const outputLength = Math.floor((clean.length * 3) / 4) - padding;
+    const bytes = new Uint8Array(outputLength);
+    const chunkSize = 4 * 16384;
+
+    let writeOffset = 0;
+    for (let offset = 0; offset < clean.length; offset += chunkSize) {
+        if (shouldCancel?.()) {
+            throw new Error("Analysis cancelled");
+        }
+
+        const chunk = clean.slice(offset, Math.min(clean.length, offset + chunkSize));
+        const binary = atob(chunk);
+        for (let i = 0; i < binary.length; i++) {
+            bytes[writeOffset++] = binary.charCodeAt(i);
+        }
+
+        if ((offset / chunkSize) % 4 === 0) {
+            await nextUiTick();
+        }
     }
+
     return bytes.buffer;
 }
 
@@ -40,13 +65,63 @@ let sessionSelectedFilePath = "";
 let sessionError: string | null = null;
 let sessionSamples: Float32Array | null = null;
 
+interface ProgressState {
+    percent: number;
+    message: string;
+}
+
+const DEFAULT_PROGRESS_STATE: ProgressState = {
+    percent: 0,
+    message: "Preparing analysis...",
+};
+
+interface CancelToken {
+    cancelled: boolean;
+}
+
+function cancelToken(tokenRef: MutableRefObject<CancelToken | null>): void {
+    if (tokenRef.current) {
+        tokenRef.current.cancelled = true;
+        tokenRef.current = null;
+    }
+}
+
+function createToken(tokenRef: MutableRefObject<CancelToken | null>): CancelToken {
+    cancelToken(tokenRef);
+    const token: CancelToken = { cancelled: false };
+    tokenRef.current = token;
+    return token;
+}
+
+function isCancelledError(error: unknown): boolean {
+    return error instanceof Error && error.message === "Analysis cancelled";
+}
+
+function toProgressState(progress: AnalysisProgress): ProgressState {
+    return {
+        percent: Math.round(Math.max(0, Math.min(100, progress.percent))),
+        message: progress.message,
+    };
+}
+
 export function useAudioAnalysis() {
     const [analyzing, setAnalyzing] = useState(false);
+    const [analysisProgress, setAnalysisProgress] = useState<ProgressState>(DEFAULT_PROGRESS_STATE);
     const [result, setResult] = useState<AnalysisResult | null>(() => sessionResult);
     const [selectedFilePath, setSelectedFilePath] = useState(() => sessionSelectedFilePath);
     const [error, setError] = useState<string | null>(() => sessionError);
     const [spectrumLoading, setSpectrumLoading] = useState(false);
+    const [spectrumProgress, setSpectrumProgress] = useState<ProgressState>(DEFAULT_PROGRESS_STATE);
     const samplesRef = useRef<Float32Array | null>(sessionSamples);
+    const analysisTokenRef = useRef<CancelToken | null>(null);
+    const spectrumTokenRef = useRef<CancelToken | null>(null);
+
+    useEffect(() => {
+        return () => {
+            cancelToken(analysisTokenRef);
+            cancelToken(spectrumTokenRef);
+        };
+    }, []);
 
     const setResultWithSession = useCallback((next: AnalysisResult | null) => {
         sessionResult = next;
@@ -69,7 +144,13 @@ export function useAudioAnalysis() {
             return null;
         }
 
+        const token = createToken(analysisTokenRef);
+        cancelToken(spectrumTokenRef);
         setAnalyzing(true);
+        setAnalysisProgress({
+            percent: 1,
+            message: "Preparing file...",
+        });
         setErrorWithSession(null);
         setResultWithSession(null);
         setSelectedFilePathWithSession(file.name);
@@ -81,7 +162,14 @@ export function useAudioAnalysis() {
             const payload = await analyzeFlacFile(file, {
                 fftSize: prefs.fftSize,
                 windowFunction: prefs.windowFunction,
-            });
+            }, (progress) => {
+                if (token.cancelled) return;
+                setAnalysisProgress(toProgressState(progress));
+            }, () => token.cancelled);
+
+            if (token.cancelled) {
+                return null;
+            }
 
             samplesRef.current = payload.samples;
             sessionSamples = payload.samples;
@@ -91,15 +179,25 @@ export function useAudioAnalysis() {
             logger.success(`Audio analysis completed in ${elapsed}s`);
             return payload.result;
         } catch (err) {
+            if (isCancelledError(err)) {
+                return null;
+            }
             const errorMessage = err instanceof Error ? err.message : "Failed to analyze audio file";
             logger.error(`Analysis error: ${errorMessage}`);
             setErrorWithSession(errorMessage);
+            setAnalysisProgress({
+                percent: 0,
+                message: "Analysis failed",
+            });
             toast.error("Audio Analysis Failed", {
                 description: errorMessage,
             });
             return null;
         } finally {
-            setAnalyzing(false);
+            if (analysisTokenRef.current === token) {
+                analysisTokenRef.current = null;
+                setAnalyzing(false);
+            }
         }
     }, [setErrorWithSession, setResultWithSession, setSelectedFilePathWithSession]);
 
@@ -109,7 +207,13 @@ export function useAudioAnalysis() {
             return null;
         }
 
+        const token = createToken(analysisTokenRef);
+        cancelToken(spectrumTokenRef);
         setAnalyzing(true);
+        setAnalysisProgress({
+            percent: 1,
+            message: "Reading file from disk...",
+        });
         setErrorWithSession(null);
         setResultWithSession(null);
         setSelectedFilePathWithSession(filePath);
@@ -126,8 +230,23 @@ export function useAudioAnalysis() {
                 throw new Error("ReadFileAsBase64 backend method is unavailable");
             }
 
-            const base64Data = await readFileAsBase64(filePath);
-            const arrayBuffer = base64ToArrayBuffer(base64Data);
+            let base64Data = await readFileAsBase64(filePath);
+            if (token.cancelled) {
+                return null;
+            }
+            setAnalysisProgress({
+                percent: 10,
+                message: "File loaded",
+            });
+            const arrayBuffer = await base64ToArrayBuffer(base64Data, () => token.cancelled);
+            base64Data = "";
+            if (token.cancelled) {
+                return null;
+            }
+            setAnalysisProgress({
+                percent: 15,
+                message: "Preparing audio buffer...",
+            });
             const fileName = fileNameFromPath(filePath);
             const payload = await analyzeFlacArrayBuffer(
                 {
@@ -139,8 +258,21 @@ export function useAudioAnalysis() {
                     fftSize: prefs.fftSize,
                     windowFunction: prefs.windowFunction,
                 },
+                (progress) => {
+                    if (token.cancelled) return;
+                    const mappedPercent = 10 + (progress.percent * 0.9);
+                    setAnalysisProgress({
+                        percent: Math.round(Math.max(0, Math.min(100, mappedPercent))),
+                        message: progress.message,
+                    });
+                },
+                () => token.cancelled,
             );
 
+            if (token.cancelled) {
+                return null;
+            }
+
             samplesRef.current = payload.samples;
             sessionSamples = payload.samples;
             setResultWithSession(payload.result);
@@ -149,58 +281,98 @@ export function useAudioAnalysis() {
             logger.success(`Audio analysis completed in ${elapsed}s`);
             return payload.result;
         } catch (err) {
+            if (isCancelledError(err)) {
+                return null;
+            }
             const errorMessage = err instanceof Error ? err.message : "Failed to analyze audio file";
             logger.error(`Analysis error: ${errorMessage}`);
             setErrorWithSession(errorMessage);
+            setAnalysisProgress({
+                percent: 0,
+                message: "Analysis failed",
+            });
             toast.error("Audio Analysis Failed", {
                 description: errorMessage,
             });
             return null;
         } finally {
-            setAnalyzing(false);
+            if (analysisTokenRef.current === token) {
+                analysisTokenRef.current = null;
+                setAnalyzing(false);
+            }
         }
     }, [setErrorWithSession, setResultWithSession, setSelectedFilePathWithSession]);
 
     const reAnalyzeSpectrum = useCallback(async (fftSize: number, windowFunction: string) => {
         if (!result || !samplesRef.current) return;
 
+        const token = createToken(spectrumTokenRef);
         setSpectrumLoading(true);
+        setSpectrumProgress({
+            percent: 0,
+            message: "Preparing FFT...",
+        });
         try {
-            const spectrum = analyzeSpectrumFromSamples(samplesRef.current, result.sample_rate, {
+            await new Promise<void>((resolve) => setTimeout(resolve, 0));
+            const spectrum = await analyzeSpectrumFromSamples(samplesRef.current, result.sample_rate, {
                 fftSize,
                 windowFunction: toWindowFunction(windowFunction),
-            });
+            }, (progress) => {
+                if (token.cancelled) return;
+                setSpectrumProgress(toProgressState(progress));
+            }, () => token.cancelled);
+
+            if (token.cancelled) {
+                return;
+            }
             setResult((prev) => {
                 const next = prev ? { ...prev, spectrum } : prev;
                 sessionResult = next;
                 return next;
             });
         } catch (err) {
+            if (isCancelledError(err)) {
+                return;
+            }
             const errorMessage = err instanceof Error ? err.message : "Failed to re-analyze spectrum";
             logger.error(`Spectrum re-analysis error: ${errorMessage}`);
+            setSpectrumProgress({
+                percent: 0,
+                message: "Spectrum analysis failed",
+            });
             toast.error("Spectrum Analysis Failed", {
                 description: errorMessage,
             });
         } finally {
-            setSpectrumLoading(false);
+            if (spectrumTokenRef.current === token) {
+                spectrumTokenRef.current = null;
+                setSpectrumLoading(false);
+            }
         }
     }, [result]);
 
     const clearResult = useCallback(() => {
+        cancelToken(analysisTokenRef);
+        cancelToken(spectrumTokenRef);
+        setAnalyzing(false);
         setResultWithSession(null);
         setErrorWithSession(null);
         setSelectedFilePathWithSession("");
         setSpectrumLoading(false);
+        setAnalysisProgress(DEFAULT_PROGRESS_STATE);
+        setSpectrumProgress(DEFAULT_PROGRESS_STATE);
         samplesRef.current = null;
         sessionSamples = null;
     }, [setErrorWithSession, setResultWithSession, setSelectedFilePathWithSession]);
 
     return {
         analyzing,
+        analysisProgress,
         result,
         error,
         selectedFilePath,
         spectrumLoading,
+        spectrumProgress,
         analyzeFile,
         analyzeFilePath,
         reAnalyzeSpectrum,
diff --git a/frontend/src/lib/flac-analysis.ts b/frontend/src/lib/flac-analysis.ts
index 7eb2c33..6f2d06a 100644
--- a/frontend/src/lib/flac-analysis.ts
+++ b/frontend/src/lib/flac-analysis.ts
@@ -10,6 +10,9 @@ const DEFAULT_PARAMS: SpectrumParams = {
     windowFunction: "hann",
 };
 
+const MAX_SPECTRUM_FRAMES = 2200;
+const METRICS_CHUNK_SIZE = 262144;
+
 interface FlacStreamInfo {
     sampleRate: number;
     channels: number;
@@ -29,6 +32,49 @@ export interface FlacArrayBufferInput {
     arrayBuffer: ArrayBuffer;
 }
 
+export type AnalysisPhase = "read" | "parse" | "decode" | "metrics" | "spectrum" | "finalize";
+
+export interface AnalysisProgress {
+    phase: AnalysisPhase;
+    percent: number;
+    message: string;
+}
+
+export type AnalysisProgressCallback = (progress: AnalysisProgress) => void;
+export type AnalysisCancelCheck = () => boolean;
+
+function reportProgress(
+    callback: AnalysisProgressCallback | undefined,
+    phase: AnalysisPhase,
+    percent: number,
+    message: string,
+): void {
+    if (!callback) return;
+    const clamped = Math.max(0, Math.min(100, percent));
+    callback({
+        phase,
+        percent: clamped,
+        message,
+    });
+}
+
+function throwIfCancelled(cancelCheck?: AnalysisCancelCheck): void {
+    if (cancelCheck?.()) {
+        throw new Error("Analysis cancelled");
+    }
+}
+
+function nowMs(): number {
+    return typeof performance !== "undefined" ? performance.now() : Date.now();
+}
+
+function nextTick(): Promise<void> {
+    if (typeof requestAnimationFrame === "function") {
+        return new Promise((resolve) => requestAnimationFrame(() => resolve()));
+    }
+    return new Promise((resolve) => setTimeout(resolve, 0));
+}
+
 function parseFlacStreamInfo(buffer: ArrayBuffer): FlacStreamInfo {
     const data = new Uint8Array(buffer);
     if (data.length < 4 || data[0] !== 0x66 || data[1] !== 0x4c || data[2] !== 0x61 || data[3] !== 0x43) {
@@ -111,8 +157,7 @@ function buildWindowCoefficients(size: number, windowFunction: SpectrumParams["w
 
 function buildBitReversal(size: number): Uint32Array {
     let bits = 0;
-    while ((1 << bits) < size)
-        bits++;
+    while ((1 << bits) < size) bits++;
 
     const out = new Uint32Array(size);
     for (let i = 0; i < size; i++) {
@@ -172,15 +217,19 @@ function fftInPlace(real: Float32Array, imag: Float32Array, bitReversal: Uint32A
     }
 }
 
-export function analyzeSpectrumFromSamples(
+export async function analyzeSpectrumFromSamples(
     samples: Float32Array,
     sampleRate: number,
     params: SpectrumParams,
-): SpectrumData {
+    onProgress?: AnalysisProgressCallback,
+    shouldCancel?: AnalysisCancelCheck,
+): Promise<SpectrumData> {
+    throwIfCancelled(shouldCancel);
     const fftSize = params.fftSize;
     const hopSize = Math.max(1, Math.floor(fftSize / 4));
     const rawWindows = Math.floor((samples.length - fftSize) / hopSize);
     const numWindows = Math.max(1, rawWindows);
+    const frameStride = Math.max(1, Math.ceil(numWindows / MAX_SPECTRUM_FRAMES));
     const freqBins = Math.floor(fftSize / 2) + 1;
     const duration = sampleRate > 0 ? samples.length / sampleRate : 0;
     const maxFreq = sampleRate / 2;
@@ -191,9 +240,24 @@ export function analyzeSpectrumFromSamples(
     const imag = new Float32Array(fftSize);
     const invFFTSizeSquared = 1 / (fftSize * fftSize);
 
-    const timeSlices: TimeSlice[] = new Array(numWindows);
-    for (let i = 0; i < numWindows; i++) {
-        const start = i * hopSize;
+    reportProgress(onProgress, "spectrum", 0, "Preparing FFT...");
+    const windowIndices: number[] = [];
+    for (let windowIndex = 0; windowIndex < numWindows; windowIndex += frameStride) {
+        windowIndices.push(windowIndex);
+    }
+    if (windowIndices[windowIndices.length - 1] !== numWindows - 1) {
+        windowIndices.push(numWindows - 1);
+    }
+
+    const totalSlices = windowIndices.length;
+    const timeSlices: TimeSlice[] = new Array(totalSlices);
+    let lastReportedPercent = -1;
+    let lastYieldAt = nowMs();
+
+    for (let i = 0; i < totalSlices; i++) {
+        throwIfCancelled(shouldCancel);
+        const windowIndex = windowIndices[i];
+        const start = windowIndex * hopSize;
         const remaining = samples.length - start;
         const copyLen = Math.max(0, Math.min(fftSize, remaining));
 
@@ -208,7 +272,7 @@ export function analyzeSpectrumFromSamples(
 
         fftInPlace(real, imag, bitReversal);
 
-        const magnitudes = new Array<number>(freqBins);
+        const magnitudes = new Float32Array(freqBins);
         for (let j = 0; j < freqBins; j++) {
             const power = (real[j] * real[j] + imag[j] * imag[j]) * invFFTSizeSquared;
             magnitudes[j] = power > 1e-12 ? 10 * Math.log10(power) : -120;
@@ -218,8 +282,24 @@ export function analyzeSpectrumFromSamples(
             time: sampleRate > 0 ? start / sampleRate : 0,
             magnitudes,
         };
+
+        const currentPercent = Math.floor(((i + 1) / totalSlices) * 100);
+        if (currentPercent > lastReportedPercent) {
+            lastReportedPercent = currentPercent;
+            reportProgress(onProgress, "spectrum", currentPercent, "Analyzing spectrum...");
+        }
+
+        if ((i + 1) % 8 === 0) {
+            const now = nowMs();
+            if (now - lastYieldAt >= 16) {
+                await nextTick();
+                lastYieldAt = nowMs();
+                throwIfCancelled(shouldCancel);
+            }
+        }
     }
 
+    reportProgress(onProgress, "spectrum", 100, "Spectrum analysis complete");
     return {
         time_slices: timeSlices,
         sample_rate: sampleRate,
@@ -232,8 +312,14 @@ export function analyzeSpectrumFromSamples(
 export async function analyzeFlacFile(
     file: File,
     params: SpectrumParams = DEFAULT_PARAMS,
+    onProgress?: AnalysisProgressCallback,
+    shouldCancel?: AnalysisCancelCheck,
 ): Promise<FrontendAnalysisPayload> {
+    throwIfCancelled(shouldCancel);
+    reportProgress(onProgress, "read", 2, "Reading file...");
     const arrayBuffer = await file.arrayBuffer();
+    throwIfCancelled(shouldCancel);
+    reportProgress(onProgress, "read", 10, "File loaded");
     return analyzeFlacArrayBuffer(
         {
             fileName: file.name,
@@ -241,28 +327,56 @@ export async function analyzeFlacFile(
             arrayBuffer,
         },
         params,
+        (progress) => {
+            const mappedPercent = 10 + (progress.percent * 0.9);
+            reportProgress(onProgress, progress.phase, mappedPercent, progress.message);
+        },
+        shouldCancel,
     );
 }
 
 export async function analyzeFlacArrayBuffer(
     input: FlacArrayBufferInput,
     params: SpectrumParams = DEFAULT_PARAMS,
+    onProgress?: AnalysisProgressCallback,
+    shouldCancel?: AnalysisCancelCheck,
 ): Promise<FrontendAnalysisPayload> {
+    throwIfCancelled(shouldCancel);
+    reportProgress(onProgress, "parse", 5, "Parsing FLAC metadata...");
     const streamInfo = parseFlacStreamInfo(input.arrayBuffer);
+    throwIfCancelled(shouldCancel);
+    reportProgress(onProgress, "decode", 15, "Decoding audio stream...");
     const audioContext = new AudioContext({ sampleRate: streamInfo.sampleRate });
 
     try {
         const audioBuffer = await audioContext.decodeAudioData(input.arrayBuffer.slice(0));
+        throwIfCancelled(shouldCancel);
+        reportProgress(onProgress, "decode", 35, "Audio decoded");
         const samples = audioBuffer.getChannelData(0);
 
+        reportProgress(onProgress, "metrics", 40, "Calculating peak/RMS...");
         let peak = 0;
         let sumSquares = 0;
+        let lastMetricsYieldAt = nowMs();
         for (let i = 0; i < samples.length; i++) {
+            throwIfCancelled(shouldCancel);
             const sample = samples[i];
             const absSample = Math.abs(sample);
             if (absSample > peak)
                 peak = absSample;
             sumSquares += sample * sample;
+
+            if ((i + 1) % METRICS_CHUNK_SIZE === 0 || i === samples.length - 1) {
+                const metricsProgress = 40 + (((i + 1) / samples.length) * 10);
+                reportProgress(onProgress, "metrics", metricsProgress, "Calculating peak/RMS...");
+
+                const now = nowMs();
+                if (now - lastMetricsYieldAt >= 16) {
+                    await nextTick();
+                    lastMetricsYieldAt = nowMs();
+                    throwIfCancelled(shouldCancel);
+                }
+            }
         }
 
         const peakDB = peak > 0 ? 20 * Math.log10(peak) : -120;
@@ -270,12 +384,24 @@ export async function analyzeFlacArrayBuffer(
         const rmsDB = rms > 0 ? 20 * Math.log10(rms) : -120;
         const dynamicRange = peakDB - rmsDB;
 
-        const spectrum = analyzeSpectrumFromSamples(samples, streamInfo.sampleRate, params);
+        reportProgress(onProgress, "metrics", 50, "Signal metrics complete");
+        const spectrum = await analyzeSpectrumFromSamples(
+            samples,
+            streamInfo.sampleRate,
+            params,
+            (progress) => {
+                const mappedPercent = 50 + (progress.percent * 0.45);
+                reportProgress(onProgress, "spectrum", mappedPercent, progress.message);
+            },
+            shouldCancel,
+        );
         const durationFromBuffer = audioBuffer.duration;
         const duration = durationFromBuffer > 0 ? durationFromBuffer : streamInfo.duration;
         const totalSamples = streamInfo.totalSamples > 0 ? streamInfo.totalSamples : Math.floor(duration * streamInfo.sampleRate);
 
-        return {
+        reportProgress(onProgress, "finalize", 97, "Finalizing result...");
+
+        const payload: FrontendAnalysisPayload = {
             result: {
                 file_path: input.fileName,
                 file_size: input.fileSize,
@@ -292,8 +418,10 @@ export async function analyzeFlacArrayBuffer(
             },
             samples,
         };
-    }
-    finally {
+
+        reportProgress(onProgress, "finalize", 100, "Analysis complete");
+        return payload;
+    } finally {
         await audioContext.close();
     }
 }
diff --git a/frontend/src/types/api.ts b/frontend/src/types/api.ts
index b809493..85bad41 100644
--- a/frontend/src/types/api.ts
+++ b/frontend/src/types/api.ts
@@ -155,7 +155,7 @@ export interface HealthResponse {
 }
 export interface TimeSlice {
     time: number;
-    magnitudes: number[];
+    magnitudes: number[] | Float32Array;
 }
 export interface SpectrumData {
     time_slices: TimeSlice[];