Geert Bevin, a long-time figure in the MPE world, has released Glinster, an MPE controller and AUv3 instrument for iPhone, iPad and Apple Vision Pro. As Synthtopia reported, it costs $9.99 on the App Store, and the purchase includes the AUv3 version.
Rather than repeat the launch story, this article looks at the settings the app exposes, because they are a useful tour of the choices every MPE setup involves.
How it plays
On iPhone and iPad you place your hand on the glass and notes appear under your fingers. Glinster measures hand shape and finger spacing and adapts the layout instead of imposing a fixed keyboard or grid. On Vision Pro you play in the air with bare hands. Because the surface adapts to you, the traditional problem of "hitting the right key" matters less than shaping the sound.
The MIDI options, explained
MPE channel-per-note or single-channel mode. MPE works by giving each sounding note its own MIDI channel, so pitch bend and pressure apply to that note alone. Glinster offers the full channel-per-note mode and a single-channel mode. Use channel-per-note for MPE-aware instruments. Use single-channel only when you are driving a synth that does not understand MPE, accepting that bend will affect every note together.
The Send MCM button. This sends MPE Configuration Message data, which tells a receiving instrument which channels form the MPE zone. If a synth does not respond as expected after you connect it, sending the configuration again is a sensible first step. See our guide to MPE channel zones.
Pitch bend range. Options are 2, 12, 24, 48 or 96 semitones. The golden rule is that the controller and the instrument must agree. MPE's default per-note range is 48 semitones, so that is the usual starting point. If glides land on the wrong pitch, mismatched ranges are the likely cause, as detailed in our pitch bend range fix guide.
Volume and brightness sources. Glinster can drive these from channel pressure or from CC 7, 11, 74 and 1. CC 74 is the standard MPE "slide" or timbre dimension, which most MPE synths map to brightness by default. Channel pressure carries per-note pressure in MPE mode. Pick what your target instrument actually listens to.
Scales, roots and tuning. The app includes 16 scales and 12 roots, with a reference pitch from 432 to 446 Hz and a two-octave shift either way. Playing in a scale is a good way to keep a freeform surface musical.
Getting it into your setup
Glinster can act as a virtual MIDI source, send to other apps on the device, and connect over Bluetooth LE MIDI or Apple network MIDI, which gives you several routes into a Mac or another iPad. Bluetooth is convenient, but expect more latency than a cable. Our article on MPE over Bluetooth MIDI covers the trade-offs, and our iPad AUv3 hosts guide helps if you plan to run it inside a host.
It also records takes as 32-bit float WAV and can play them back with the instrument live, a handy way to capture ideas before you wire everything up.
Why it is worth a look
At ten dollars, Glinster is an inexpensive way to experiment with MPE if you do not own dedicated hardware, and an interesting experiment in adaptive playing surfaces if you do. It will not replace a purpose-built controller such as the Expressive E Osmose or LinnStrument, but it shows how far expressive input can go when the interface adapts to the hand rather than the other way around.