MIDI Polyphonic Expression (MPE)

One of the biggest recent developments in MIDI is MIDI Polyphonic Expression (MPE). MPE is a method of using MIDI which enables multidimensional controllers to control multiple parameters of every note within MPE-compatible software. 

In normal MIDI, channel-wide messages (such as pitch bend) are applied to all notes being played on a single channel. In MPE, each note is assigned its own channel so that those messages can be applied to each note individually.

 The full specifications of MPE are being finalised by the MMA's MPE working group and will be published in the coming months. In the meantime, here is the background on MPE. 

This specification aims to provide an agreed method for hardware and software manufacturers to communicate multidimensional control data between MIDI controllers, synthesizers, digital audio workstations, and other products, using the existing framework of MIDI 1.0.

These proposed conventions define a way of distributing polyphonic music over a group of MIDI Channels, making multiple parameters of different notes separately controllable. This will enable richer communication between increasingly expressive MIDI hardware and software.

Briefly, what is defined is as follows:

Wherever possible, every sounding note is temporarily assigned its own MIDI Channel between its Note On and Note
Off. This allows Control Change and Pitch Bend messages to be addressed to that particular note.

A Registered Parameter Number is used to establish the range of Channels used for sending or receiving notes. Two messages
control the division of MIDI Channel space into sub-spaces called Zones, so that multi-timbral playing is still possible using only one physical MIDI interface.

When there are more active notes in a Zone than available Channels, two or more notes will have to share the same Channel.
Under such circumstances, all notes will continue to sound, but will no longer be uniquely controllable.

Each Zone has a dedicated extra Channel, called the Master Channel, which conveys common information including Program
Change messages, pedal data, and overall Pitch Bend. These messages apply across the entire Zone.

(The MPE specification also defines how to handle Pitch Bend, Aftertouch and CC messages to provide maximum interoperability.)

from the MIDI Manufacturers Association MPE Draft Specification Background Section

Digital audio workstations (DAWs) compatible with MPE

• Bitwig 8-Track & Studio
  
• GarageBand
  
• Logic Pro X
  
• Reaper
  
• Steinberg Cubase
  
• Tracktion Waveform

MIDI Controllers Compatible with MPE

•  ROLI- Seaboard, Blocks
  
• Eigenharp
• Joue
• Linnstrument
  
• K-Board Pro 4
• Soundplane
• Touchkeys

Software synthesizers compatible with MPE

•  Admiral Quality Poly-Ana
  
• Cycling '74 Max
  
• Equator / Equator Player
  
• FXpansion Strobe2
  
• KV331 Audio SynthMaster
  
• Madrona Labs Aalto
  
• Madrona Labs Kaivo
  
• MainStage
  
• UVI Falcon
  
• The Music Room
  
• Native Instruments Reaktor
  
• Softube Modular
  
• Spitfire BT Phobos
  
• Stagecraft Addiction
  
• Symbolic Sound Kyma
  
• UVI Falcon
  

Mobile apps compatible with MPE

• NOISE
  
• Seaboard 5D
  
• Wizdom Music: GeoShred, Geo Synthesizer, SampleWiz 
  
• GarageBand iOS
  
• Christophe Duquesne: SpringSound
  
• Jesper Nordin: Gestrument
  
• KV331 Audio: Synthmaster Player
  
• Moog Music: Model 15 Modular, AniMoog
  
• Ngo Minh Ngoc: iFretless Bass, Sax, iFretless Guitar​
• One Red Dog Media: Arctic ProSynth
  
• PPG Apps: WaveGenerator & WaveMapper
  
• Sonosaurus: ThumbJam, DrumJam

Hardware synthesizers compatible with MPE

• ​​​​​Axoloti
  
• Deckard's Dream
  
• Endorphin.es Shuttle Control
  
• Expert Sleepers FH-1
  
• Futuresonus Parva
  
• Haken Contiuum
  
• MOD Duo
  
• Modal Electronics 001 / 002 / 002R
  
• Modor NF-1 / NF-1m
  

Here is a collection of Youtube videos showing off how expressive MPE enabled instruments can be. 

Links to online MPE resources