diff --git a/frontend/lib/api.ts b/frontend/lib/api.ts
new file mode 100644
index 0000000..c1d25a5
--- /dev/null
+++ b/frontend/lib/api.ts
@@ -0,0 +1,103 @@
+/**
+ * API client for Audio Classifier backend
+ */
+import axios from 'axios'
+import type {
+  Track,
+  TracksResponse,
+  SearchResponse,
+  SimilarTracksResponse,
+  JobStatus,
+  AnalyzeFolderRequest,
+  WaveformData,
+  Stats,
+  FilterParams,
+} from './types'
+
+const API_BASE_URL = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:8000'
+
+const apiClient = axios.create({
+  baseURL: API_BASE_URL,
+  headers: {
+    'Content-Type': 'application/json',
+  },
+})
+
+// Tracks
+export async function getTracks(params: FilterParams & { skip?: number; limit?: number }): Promise<TracksResponse> {
+  const response = await apiClient.get('/api/tracks', { params })
+  return response.data
+}
+
+export async function getTrack(id: string): Promise<Track> {
+  const response = await apiClient.get(`/api/tracks/${id}`)
+  return response.data
+}
+
+export async function deleteTrack(id: string): Promise<void> {
+  await apiClient.delete(`/api/tracks/${id}`)
+}
+
+// Search
+export async function searchTracks(
+  query: string,
+  filters?: { genre?: string; mood?: string; limit?: number }
+): Promise<SearchResponse> {
+  const response = await apiClient.get('/api/search', {
+    params: { q: query, ...filters },
+  })
+  return response.data
+}
+
+// Similar
+export async function getSimilarTracks(id: string, limit: number = 10): Promise<SimilarTracksResponse> {
+  const response = await apiClient.get(`/api/tracks/${id}/similar`, {
+    params: { limit },
+  })
+  return response.data
+}
+
+// Analysis
+export async function analyzeFolder(request: AnalyzeFolderRequest): Promise<{ job_id: string }> {
+  const response = await apiClient.post('/api/analyze/folder', request)
+  return response.data
+}
+
+export async function getAnalyzeStatus(jobId: string): Promise<JobStatus> {
+  const response = await apiClient.get(`/api/analyze/status/${jobId}`)
+  return response.data
+}
+
+export async function deleteJob(jobId: string): Promise<void> {
+  await apiClient.delete(`/api/analyze/job/${jobId}`)
+}
+
+// Audio
+export function getStreamUrl(trackId: string): string {
+  return `${API_BASE_URL}/api/audio/stream/${trackId}`
+}
+
+export function getDownloadUrl(trackId: string): string {
+  return `${API_BASE_URL}/api/audio/download/${trackId}`
+}
+
+export async function getWaveform(trackId: string, numPeaks: number = 800): Promise<WaveformData> {
+  const response = await apiClient.get(`/api/audio/waveform/${trackId}`, {
+    params: { num_peaks: numPeaks },
+  })
+  return response.data
+}
+
+// Stats
+export async function getStats(): Promise<Stats> {
+  const response = await apiClient.get('/api/stats')
+  return response.data
+}
+
+// Health
+export async function healthCheck(): Promise<{ status: string }> {
+  const response = await apiClient.get('/health')
+  return response.data
+}
+
+export default apiClient
diff --git a/frontend/lib/types.ts b/frontend/lib/types.ts
new file mode 100644
index 0000000..d3b4614
--- /dev/null
+++ b/frontend/lib/types.ts
@@ -0,0 +1,111 @@
+/**
+ * TypeScript type definitions for Audio Classifier
+ */
+
+export interface Track {
+  id: string
+  filepath: string
+  filename: string
+  duration_seconds: number
+  file_size_bytes: number
+  format: string
+  analyzed_at: string
+
+  features: {
+    tempo_bpm: number
+    key: string
+    time_signature: string
+    energy: number
+    danceability: number
+    valence: number
+    loudness_lufs: number
+    spectral_centroid: number
+    zero_crossing_rate: number
+  }
+
+  classification: {
+    genre: {
+      primary: string
+      secondary: string[]
+      confidence: number
+    }
+    mood: {
+      primary: string
+      secondary: string[]
+      arousal: number
+      valence: number
+    }
+    instruments: string[]
+    vocals: {
+      present: boolean | null
+      gender: string | null
+    }
+  }
+
+  embedding: {
+    model: string | null
+    dimension: number | null
+  }
+
+  metadata: Record<string, any>
+}
+
+export interface FilterParams {
+  genre?: string
+  mood?: string
+  bpm_min?: number
+  bpm_max?: number
+  energy_min?: number
+  energy_max?: number
+  has_vocals?: boolean
+  sort_by?: 'analyzed_at' | 'tempo_bpm' | 'duration_seconds' | 'filename' | 'energy'
+  sort_desc?: boolean
+}
+
+export interface TracksResponse {
+  tracks: Track[]
+  total: number
+  skip: number
+  limit: number
+}
+
+export interface SearchResponse {
+  query: string
+  tracks: Track[]
+  total: number
+}
+
+export interface SimilarTracksResponse {
+  reference_track_id: string
+  similar_tracks: Track[]
+  total: number
+}
+
+export interface JobStatus {
+  job_id: string
+  status: 'pending' | 'running' | 'completed' | 'failed'
+  progress: number
+  total: number
+  current_file: string | null
+  errors: Array<{ file?: string; error: string }>
+  saved_count?: number
+}
+
+export interface AnalyzeFolderRequest {
+  path: string
+  recursive: boolean
+}
+
+export interface WaveformData {
+  peaks: number[]
+  duration: number
+  num_peaks: number
+}
+
+export interface Stats {
+  total_tracks: number
+  genres: Array<{ genre: string; count: number }>
+  moods: Array<{ mood: string; count: number }>
+  average_bpm: number
+  total_duration_hours: number
+}
diff --git a/frontend/lib/utils.ts b/frontend/lib/utils.ts
new file mode 100644
index 0000000..c2304dd
--- /dev/null
+++ b/frontend/lib/utils.ts
@@ -0,0 +1,27 @@
+import { type ClassValue, clsx } from "clsx"
+import { twMerge } from "tailwind-merge"
+
+export function cn(...inputs: ClassValue[]) {
+  return twMerge(clsx(inputs))
+}
+
+export function formatDuration(seconds: number): string {
+  const mins = Math.floor(seconds / 60)
+  const secs = Math.floor(seconds % 60)
+  return `${mins}:${secs.toString().padStart(2, '0')}`
+}
+
+export function formatFileSize(bytes: number): string {
+  if (bytes < 1024) return `${bytes} B`
+  if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`
+  if (bytes < 1024 * 1024 * 1024) return `${(bytes / (1024 * 1024)).toFixed(1)} MB`
+  return `${(bytes / (1024 * 1024 * 1024)).toFixed(1)} GB`
+}
+
+export function formatBPM(bpm: number): string {
+  return `${Math.round(bpm)} BPM`
+}
+
+export function formatPercentage(value: number): string {
+  return `${Math.round(value * 100)}%`
+}