IPSI, the isomorphic pitch shifting interface, comprises a custom USB-MIDI footpedal interface and accompanying pitch-shifting software patches built in Max/MSP.

The system allows a solo instrumental performer such as a woodwind or brass player to add pitch-shifted intervals to their live performance, harmonising their playing with virtually any chromatic voicing over a 2.5 octave range.

Unlike commercial harmonisation systems, IPSI gives the player complete agency over the structure and diatonicity of the chords produced - in real time a player can dynamically switch from dense atonal clusters, to wide open quartal or quintal voicings as well as typical major/minor/7th chords and single intervals.

An envelope-driven mixer gives the harmonised voices a dynamic shape over time, and eight side-mounted potentiometers can be mapped to control elements of the pitch-shifting software or any other MIDI-controllable parameters.

Remote thumbswitches connected via an RJ45 port can trigger looping devices, toggle effects or enable an “audio freeze” to provide a static input signal for pitch shifting - independent of the live instrumental performance.