A stem mixer for iPhone

Reference Anywhere.
A/B Everything.

AB:X is a stem mixer for iPhone. Change your mix in the car while it plays, then export notes for your DAW.

Explore the app
The AB:X stem mixer in Studio Light.
AB:X on iPhone: fourteen named stems in the mixer, with meters, solo and mute controls, and the playing transport.
AB:X lead vocal EQ in Stage Dark.
Stems
32 max
Fader range
−40 to +20 dB
EQ
4 bands per stem
References
8 slots
Platform
iOS 17+

AB:X lets you change01 the balance while the whole mix plays, shape02 every stem with its own EQ, compare03 with a reference without a gap, and take04 your changes back to your DAW.

01Stem balance

Change the balance

Bring your stems from your DAW. Adjust each level while the whole mix plays, or use solo and mute to hear one part.

Flip EDIT to BASE to hear the mix before your changes. Playback keeps going.

Stems per project
32 max
Fader range
−40 to +20 dB

On every stem

  • Fader, −40 to +20 dB
  • Solo and mute
  • BYPASS: tap to latch, hold to hear it the other way
  • Reads change from base, or loudness in LUFS
The AB:X mixer in Stage Dark: fourteen stems with level meters, solo and mute.
The same mixer in both appearances · Development screens

02Per-stem EQ

EQ on
every stem

Open a stem and move its bands directly on the graph, over the stem’s own spectrum. Four bands on every stem, each with frequency, gain and Q.

BYPASS takes the change out while the mix keeps playing.

Lead vocal stem header: name, level meter, SOLO and MUTE.

The stemIts name, level meter, SOLO and MUTE stay on top while you edit.

BYPASS and RESET keys, and the stem level, +0.0 dB.

Bypass and resetTake the EQ out to hear the difference, or return every band to flat.

AB:X lead vocal EQ on iPhone: four bands over the spectrum, with band three selected at 3k Hz and −4.7 dB.
Band three cutting 4.7 dB at 3 kHz, drawn over the vocal’s spectrum.

On the graphBand 3 cuts 4.7 dB at 3 kHz, drawn over the vocal’s own spectrum.

Selected band: number 3, BELL shape, Q dial, 3k Hz, −4.7 dB.

The bandNumber, shape, Q, frequency and gain of the band under your finger.

On each stem
Four parametric bands
Shapes
Bell, shelf, tilt; cuts on the outer bands, band pass in the middle
While playing
BYPASS, tap or hold

03References & versions

Compare with a reference

Line up the choruses, then switch MIX to REF without a gap. Or load finished mixes into Test and compare them without their names.

AB:X stem mix in Stage Dark, with MIX selected in the transport.
Your mix, with every stem playing · Development screen

04Audio & mix notes

Take your changes back

Export the whole mix or one loop as 24-bit WAV or AAC, with a text file of your fader moves and EQ settings.

Changes Only lists what you moved. Full Settings lists every control. Use the notes to recreate the changes in your DAW.

  • .WAV24-bit
  • .AACAudio
  • .TXTMix notes
Night Drive v7.txt 
AB:X Mix Notes
Audio File: Night Drive v7.wav
Stem Input Gain: +0.0 dB
Master EQ: Bypassed
Master Limiter Input: +0.0 dB
Master Limiter Ceiling: -1.0 dBFS
Limiter Unity Gain: Off
Output Gain: +0.0 dB
Export Range: 0:00–3:42

[Kick]
- Volume: +1.5 dB

[Snare]
- No changes

[Lead Vox]
- Volume: +1.0 dB
- EQ Band 1 (Low Shelf): -2.5 dB, 150 Hz
- EQ Band 3 (Bell): -4.7 dB, 3000 Hz, Q 1.40
- EQ Band 4 (High Shelf): +2.0 dB, 9000 Hz

[FX]
- Muted: On (not included in audio export)
Example notes, in the format AB:X writes them

Under the hood

Two versions, always playing

Your edit and its base render side by side through the same master chain. EDIT to BASE is a 24 ms crossfade between two mixes that are already running, not a restart. The reference joins after the master chain.

Signal flow: up to 32 stems feed two lanes. EDIT runs each stem through its EQ and fader; BASE plays the stems at their base levels. Both lanes pass through the Master EQ and limiter, meet at the EDIT/BASE switch, then meet the reference at the MIX/REF switch before the output. Stemsup to 32 Stem EQ4 bands Fader−40 to +20 dB Master EQ+ limiter Master chainsame settings EDIT · BASE24 ms crossfade Referenceup to 8 MIX · REFno gap Outputto your ears EDIT · your changes BASE · before your changes Reference · joins after the master chain
  1. StemsUp to 32, started together.
  2. EDIT laneEach stem through its four-band EQ and fader, then the Master EQ and limiter.
  3. BASE laneThe same stems at their base levels, through the same master chain, running alongside.
  4. EDIT · BASEA 24 ms crossfade between the two running lanes.
  5. MIX · REFThe reference, one of up to 8, joins after the master chain.
  6. OutputOutput gain sits after the join, so it moves both sides equally.

Also on the surface

Lattice

Every stem placed by where its sound sits, left to right, and how loud it is, bottom to top. Drag a node up or down for level, sideways for tone.

Master EQ

Draw the line the Master EQ would need to follow your reference’s tone, then match 30, 60 or 100%.

A–B loops

Loop a passage of the mix, and of each reference, separately.

A reference waveform with loop brackets at either end and the playhead in the middle.

12

Snapshots

Name a mix state and keep changing. Restore it within the same project.

Projects

Audio and every setting kept together. Autosaves after the first named save.

Background playback

Keep listening with the screen locked, from the lock screen or AirPods.

Undo and redo

Every change is one step, including a move on the Lattice.

Demo stems

Load four sample stems and try the mixer before importing your own.

Specifications

In numbers.

Stems
Up to 32, started together
Imports
WAV, AIFF, CAF, FLAC, ALAC, M4A, MP4, MP3, AAC
Faders
−40 to +20 dB, per stem
Stem EQ
Four bands: bell, shelf, tilt, cut, band pass
Master
Master EQ with tone match, limiter
References
Up to 8, each with its own playhead and loop
Test
Up to 8 finished mixes, with BLIND
Snapshots
12 per project
Export
24-bit WAV or AAC, whole mix or A–B loop
Notes
.txt, Changes Only or Full Settings
Platform
iPhone, iOS 17 or later
Availability
December 2026

A few practical details

Before you import

How do I load my stems?

Export them from the same start point, including any leading silence, then choose a folder or select files in AB:X. It starts the files together; it does not align them for you. For cloud storage, selecting files is more reliable than importing a folder.

Does AB:X replace my DAW?

No. Use your DAW to record and arrange, then bring stems into AB:X to try changes to the mix.

How do I take changes back?

Export a 24-bit WAV or AAC mix with optional text notes of your settings and changes. Use the notes to recreate adjustments in your DAW; they do not update the DAW session automatically.

Which devices does it support?

iPhone running iOS 17 or later.

Coming to iPhone · December 2026

Reference Anywhere.
A/B Everything.

Launch email only. Privacy

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Stem mixer

Real development screen