You can get the feeling of “pushing into” an iPhone as of the iPhone 6S. It’s an expressive, intimate gesture, which is generally used for … wait, really, shortcut menus? That’s pretty boring.

Ever since I saw the feature, I wanted to see it used for music applications. And one obvious fit is an emerging standard for sending expressive pressure-based control over MIDI.

The futuristic, sleek black ROLI Seaboard does it. The lovely, wooden Madrona Labs Soundplane does it. Roger Linn’s innovative grid-covered Linnstrument does it. It’s all a (draft) specification for control called MPE – Multidimensional Polyphonic Expression. (Early on, people wanted to dub this “expressive MIDI,” but that might imply that MIDI is somehow not normally expressive, when it is.)

MPE is cool because in addition to velocity (when you hit a note) or only monophonic pressure (like channel aftertouch), it lets you send additional control data for everything. Maybe your pinkie is pushing a little less than your ring finger, and so on.

Aftertouch is an app that uses the iPhone’s 3D Touch capability to send both velocity and polyphonic pressure messages. So instead of just feeling like your fingers are pressing glass, you can actually use all those different fingers as nature intended.

On its own, Aftertouch lets you play, in the author’s words, “a silly little phase mod synth.”

But you can also send actual MPE data, making this compatible with instruments like Apple’s Sculpture in Logic. (Dear Apple: why oh why is Sculpture not available on iOS?) For each finger, you send pitch bend, modulation, and pressure via MIDI. That’ll work with a MIDI interface if you’ve got one, or wirelessly with Bluetooth MIDI.

The one and only R. Kevin Nelson created the app. It’s yours for 99 cents.

And there’s a little site for it:

I’d actually been talking for some time about wanting to make a little app like this, but Mr. Nelson beat me to it. That said, I notice there are actually some things this doesn’t do or does differently, so I’m curious to hear readers talk about what they want or how they imagine using this!

And if you have a compatible device with 3D Touch, you should absolutely also download ROLI’s own app. “Noise” is actually like having a virtual Seaboard on your phone or iPad. You can use it as a sound bank for the hardware, or take it on the go and practice the keyboard technique in miniature. It’s really clever, and I’m happy to own it along with my Seaboard RISE.

Noise is free and native both on iPad and iPhone. (If you’ve got an iPad Pro, by the way, Apple Pencil supports 3D Touch, though I’m not sure it’ll make so much sense here!) The ROLI app lacks MIDI output, though, so it’s not direct competition for Aftertouch. It’s worth having both.

Noise on App Store

ROLI have written up a little guide to recommend apps for Seaboard owners which is worth a look: