Four track digital recorder and editor

A pocket tape machine for iPhone. Spin the disc, scrub the tape, overdub four tracks — and let your groovebox drive the recording over USB.

App Store — soon Join the beta

iPhone · iOS 26 · free beta via TestFlight

TR4 home screen: a large disc with a custom vinyl skin, tape timeline and transport controls

Made to record
your EP-133 K.O. II

Plug in over USB and TR4 recognizes the device, captures true stereo, and arms itself. Press play on the K.O. II — recording starts on the first sound. Stop the groove — the take ends, rewinds and re-arms for the next pass. Record groups A/B/C/D onto four tracks without ever touching your iPhone.

1 — PlugUSB-C. TR4 shows the device by name and waits for signal.
2 — PlayRecording starts the instant sound arrives. Zero attack lost.
3 — StopThe take ends on silence, rewinds to zero and re-arms.
4 — RepeatSwitch tracks between passes and layer your set.

What’s inside

A disc with real physicsDrag to scrub with varispeed — even in reverse. Flick it and it spins down like real hardware.
Four-track overdubRecord a track while the others play. Mute, solo, volume, pan and non-destructive crop per track.
USB stereo inClass-compliant devices record in true stereo at 48 kHz, 32-bit float.
Auto-record on USB signalThreshold-armed with noise calibration. Your hardware starts and stops the tape.
Metronome with count-in3-2-1 count-in, and a visual beat — screen pulses on the grid when the click would leak into the mic.
Disc skinsHold the disc to swap its look. Thirteen designs, from vinyl to street art.
Export anywhereMix or separate stems, as WAV, AIFF or M4A — straight to the share sheet.
Auto-saveEvery take is saved as raw audio plus edits. Reopen projects from the recents list.
TranscriptionTurn voice takes into text, in your language, on device.

On the tape

TR4 entry screen with the TR4 logo and the recent recordings list TR4 home screen with a custom disc skin TR4 disc skin picker carousel