Client-Side PDF Toolkit
100% Client-Side PDF processing. No server uploads.
About Audio Speed Changer
The Audio Speed & Tempo Changer (Time-Stretching) speeds up or slows down audio playback ($0.25\times$ to $4.0\times$) with independent Pitch Lock (WSOLA phase preservation) or classic Vinyl Resampling / Tape Varichannel effect.
How to Use Audio Speed Changer
Step 1
Upload an audio file.
Step 2
Set target playback speed (e.g. 1.25x, 1.5x, or 0.75x).
Step 3
Toggle Pitch Lock to keep vocal pitch natural.
Step 4
Click "Export Processed Audio".
Practical Use Cases for Audio Speed Changer
Speeding Up Lectures & Podcast Audio (1.25x, 1.5x, 2.0x)
Speed up long lecture recordings and voice memos while keeping the speaker's voice at its natural pitch without the "chipmunk effect".
Slowing Down Music for Instrumental Practice & Transcription
Slow down complex guitar solos or piano passages to 50% speed with preserved pitch to learn difficult musical phrases note-by-note.
Input & Output Examples
Speeding Up Audio to 1.5x with Pitch Lock
Audio: `lecture.mp3` (60 min), Speed: `1.5x`, Pitch Lock: `Enabled`
Processed Audio: `lecture_1.5x.mp3` (40 min) | Natural voice pitch preserved 100%
Key Features & Performance
- ✓Speed Multiplier slider: 0.25x (Super Slow) to 4.0x (Ultra Fast).
- ✓Modes: Pitch-Preserved Time-Stretch (WSOLA algorithm) or Classic Tape Speed / Vinyl Varichannel (changes pitch with speed).
- ✓Real-time playback speed scrub and instant audio preview.
- ✓100% Client-Side WebAssembly DSP engine.
- ✓1-Click Download speed-adjusted audio.
Key Terminology & Definitions
Time-Stretching (WSOLA)
Waveform Similarity Overlap-Add; a digital signal processing algorithm that alters audio duration without altering its pitch.
Varispeed / Tape Resampling
Altering speed and pitch proportionally, identical to speeding up or slowing down physical analog tape or vinyl records.