Numerical Audio has released a MIDI performance toolkit for iPad that pulls in every keyboard from the developer’s KB-1 Expressive Keyboard Suite, bolts on a full set of step sequencers, and lets you lay them out on a customizable touch control surface. It runs standalone or as an AUv3 plugin.
At its core, MIDIRack is a surface builder: drop keyboards, sequencers, knobs, faders, XY pads and buttons onto a snapping grid, assign them to MIDI CC, and route MIDI out to any synth, app or piece of hardware over CoreMIDI or a built-in virtual port. A polyphonic synth and drum kit are included, so it’s playable straight out of the box.
All six KB-1 keyboards are on offer — a velocity-sensitive piano, chord pads, a scale-locked keyboard, two MPE surfaces (a Seaboard-style ribbon and a Strings grid), and a 4×4 drum pad — while the sequencer side covers drum, melody, chord, analog and CC step lanes plus a note-grid Matrix, complete with per-step probability, ties, and microtiming, chainable into full arrangements with a scene launcher.
For DAW users, MIDIRack connects to Logic, Live, Bitwig, Cubase, or anything else over USB or Bluetooth MIDI with no drivers needed, with the MPE surfaces sending full pitch bend, slide, and pressure data. An optional one-time in-app purchase unlocks a visual MIDI graph editor with 60+ processing nodes, including arpeggiators, quantizers, euclidean generators, LFOs, and even generative modules like a Turing machine and Lorenz attractor.
MIDIRack is available now on the App Store for iPadOS at an introductory price of $7.99 USD for the base app and $7.99 USD for the Graph Editor unlock (regularly $14.99 USD each). The offer is valid through August 31st, 2026.
More information: Numerical Audio
