What You Need
- An iPhone or iPad on iOS 15 or later, a Mac on macOS 12 or later (Apple silicon or Intel), or an Android device on Android 7.0 or later.
- Something to chop: a WAV, AIFF, MP3, AAC or FLAC file, the soundtrack of a video, or a sound you record with the microphone.
- For stems, a network connection once, for the one-time download of the separation model (about 79 MB). After that, splitting works offline.
- Optional: a MIDI pad controller or keyboard, and on iPad or Mac an Audio Unit host such as GarageBand, to use Chopmatic as a plugin.
Getting Started
- On the CHOP tab, tap OPEN and choose an audio file, or press RECORD to record one. On iPad and Mac you can also drag a file onto the screen.
- Pick a chop mode: BARS, LOOPS, SPIKES, EQUAL or MANUAL.
- Tap a pad to hear its slice; hold it to loop. With a pad selected, the row above the pads sets its PITCH, GAIN, FILTER and REVERSE.
- On SEQUENCE, ADD FROM CHOPS puts slices in the kit, one row each. Tap cells to place hits and press PLAY, or press REC and play the pads.
- On SONG, pick a sequence below the timeline, then tap or drag along the timeline to lay it down.
- EXPORT on each tab writes what that tab makes: slices and kits from CHOP, loops from SEQUENCE and SONG.
Troubleshooting
Splitting stems fails the first time.
The first split downloads the separation model (about 79 MB), so it needs a network connection that one time. Check you are online and try again. Once the model is on your device, splitting works with no connection at all.
RECORD doesn't pick anything up.
Your device asks for microphone permission the first time you press RECORD. If it was declined, allow the microphone for Chopmatic in your device's settings, then try again.
The pads don't answer my MIDI controller.
Notes from C1 up play the pads, with no setup. If your controller sends notes in a lower octave, shift it up. To map knobs and buttons to tempo, swing, transport and the pad controls, use MIDI LEARN.
The plugin doesn't appear in my DAW.
Open the Chopmatic app once first, then look for it again in your host's instrument list. The plugin is on iPad and Mac only.
Frequently Asked
What audio can I load?
WAV, AIFF, MP3, AAC and FLAC, and the soundtrack of a video, at their own sample rate and channels. Open them from Files with OPEN, drag them onto the screen on iPad and Mac, or press RECORD to record from the microphone. A recording stays on your device and becomes a new sample to chop.
What do the chop modes do?
- BARS: slices on a tempo grid from 1/4 to 1/32 notes, with tempo DETECT, and ÷2 and ×2 for half- and double-time guesses.
- LOOPS: finds the 1, 2, 4 and 8-bar loops inside a sample that really loop.
- SPIKES: a cut on every transient, with a SENSE knob.
- EQUAL: even slices, from 4 to 64.
- MANUAL: tap the waveform to cut wherever you like, and drag any edge.
Does splitting stems upload my audio?
No. Stems are separated on your device, into drums, bass, vocals and other parts. The first time, Chopmatic downloads its separation model (about 79 MB) from our hosted copy on huggingface.co and checks it; from then on it works offline. MONO or STEREO, and a RANGE of 11 or 16 kHz, are on the SETTINGS tab. The split is made for chopping and resampling, so expect a little bleed rather than a studio master.
How do sequences and the song work?
There are 16 sequences of 1, 2, 4 or 8 bars, on a multitrack grid with a row for each chop in your kit, up to 16 tracks. Tap steps, drag to paint, or press REC and play the pads or a MIDI controller while it loops. QUANTIZED or HUMAN: every hit keeps its step on the grid and the timing you really played, so you can switch either way at any time. Each sequence has its own SWING, and the kit plays MONO or POLY. The sequence's name at the top switches, adds and duplicates sequences, and the pencil beside it renames one.
On SONG, lay sequences out on a 64-bar timeline by tapping or dragging. Press and hold a sequence and drop it on another to reorder them. UNDO and REDO, in the top bar, cover everything.
Can I use a MIDI controller?
Yes. Plug in a pad controller or keyboard and play: notes from C1 up play the pads with no setup, and you can record them into a sequence with REC. MIDI LEARN maps your knobs and buttons to tempo, swing, transport and the pad controls. On Android, connect over USB MIDI.
How do I use Chopmatic as a plugin in my DAW?
On iPad and Mac, Chopmatic is also an Audio Unit (AUv3) instrument. Open the app once first. On iPad, in GarageBand, add a new track and choose Audio Unit Extensions › Chopmatic. On the Mac, in GarageBand or Logic Pro, make a software instrument track and choose AU Instruments › Best Practice › Chopmatic. Other Audio Unit hosts list it in their own instrument menus.
OPEN in the plugin window loads a file. Your host's notes play the pads from C1, the plugin plays locked to the host's tempo and transport, and everything is saved with your project.
What can I export?
- Slices: every slice as its own WAV, as you hear it, plus ready-made kits for other samplers (SFZ, Decent Sampler and OP-1 drum kits), mapped from C1.
- Portable Kit: your pads and sequence as one web page that plays in any browser.
- Mix: a sequence or the whole song as one WAV that loops seamlessly, ringing tails included. Or RESAMPLE it into a new sample and chop that.
- Sessions: save a
.chopmaticfile and open it on another device.
On iPhone and iPad, exports go to the Chopmatic folder in the Files app.
Is there anything more to buy?
No. Chopmatic is a one-time purchase with every feature included: no in-app purchases, no subscription, no account, and no data collected.
Still Stuck
Write in. Chopmatic is made by one person, and email is the only channel — there is no ticket system and no account you need in order to ask. Contact explains what to include so it can be answered in one reply rather than five.
An Independent App
Chopmatic is an independent app and is not affiliated with the makers of Decent Sampler or the OP-1. Those names are used only to say which kit formats it exports. For problems with another app or instrument, please contact its maker.