MPE (Mid polyphonic expression)

DSP, Plug-in and Host development discussion.
4697 posts since 18 Jul, 2002 from London, UK

Post Tue Oct 22, 2019 3:32 am

They could have. The thing is NRPN (and also SysEx). Is just too open ended for what they want to do. This entails that they have to add more on specification/standardization which means that they have to convince vendors to adopt the extra new spec. The more minimal changes they make, the more probable that companies will adopt.
MPE is, in effect, an extension to the pre-existing MIDI Mode 4 ("note per channel") used by guitar controllers since the '80s. It's not perfect, but it does provide reliable transport across any kind of transparent MIDI network (whether that's a five-pin DIN wire, USB, an OS MIDI stack, Bluetooth, a plug-in API etc.) and reliable recording and playback on existing systems.

(Yes, it gets broken by hosts that re-channelize i.e. Ableton, and yes it has some problems with edit/merge operations due to channel ID conflicts and non-atomicity.. however, NRPN-based implementations have the same problem x10).

Btw, the host needs to be responsible for sending the MPE configuration message, because you might re-load the project you recorded earlier without your Seaboard connected, or send the project to a colleague, and still want the tracks to play as MPE ;)
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Markus Krause
219 posts since 2 Jul, 2018

Re: MPE (Mid polyphonic expression)

Post Tue Oct 22, 2019 3:50 am

I agree with this.

It's indeed the hosts's task to send the MPE initialisation message to the Midi receivers.

Furthermore the MPE keyboard itself should send an MPE initialisation message when it is powered on, to make all the host or midi receiver know that it is an MPE device and what configuration it uses.
Tone2 Audiosoftware

User avatar
723 posts since 31 Dec, 2008

Re: MPE (Mid polyphonic expression)

Post Tue Oct 22, 2019 4:09 am

There is no doubt about that. They used RPN as an initialization message. The context I was answering before was:
Markus Krause wrote:
Wed Aug 21, 2019 1:15 am
- Why do they not use NRPNs?
Which I assumed you meant (correctly) that they didn't use NRPN for data/parameter changes.
Last edited by S0lo on Tue Oct 22, 2019 6:02 am, edited 1 time in total.

Markus Krause
219 posts since 2 Jul, 2018

Re: MPE (Mid polyphonic expression)

Post Tue Oct 22, 2019 4:26 am

Yes. I did not refer my post to the initialisation message, but to the channel-pitchbend messages. The advantage of using NRPN / sysex would have been that the hosts would not have had to mess around with several midi-channels on one track.

I did not read the Midi 2.0 spec in detail, but it seems to do it this way. I assume that MPE will be replaced with Midi 2.0 in a couple of years.
Tone2 Audiosoftware

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