can MIDI Expression do this ?

[manki]

Got the eDRUMin in my cart already, thanks for answering my questions in its forum.

Now i'm looking through the manual of the MIDI Expression and trying to figure out if it'll work for my need
...which is very specific and a bit hard to put into words but basically what i need to do is this :

I need to have the MIDI Expression plugged in the MIDI IN and OUT of my synthesizer, and its expression input is used with an unlatching footswitch.

The synth is set to LOCAL OFF so that MIDI notes and CCs have to pass through the device in order to get back into the synth to trigger sounds and control it with its knobs.

--> When the footswitch is pressed down, it sends CC# 85, value 0,
and all the while it is held down, all midi notes passing through get +48 (transposed 4 octaves).

--> When the footswitch is released, it sends CC# 85, value 127,
and the keyboard isn't transposed anymore.

This usecase may sound weird so i can try to explain what effect needs to be achieved if anyone is curious, it has to do with getting around a limitation in Korg's Prologue 8 synth.

I was in the process of programming the workaround using an arduino board, but time is of the essence so maybe the MIDI Expression can do it.

Thank you,
Francis.

[Rob]

It can definately do one or the other. I suspect you can use a splitter to send the footswitch to two seperate inputs. You would have one toggling the transformer on and off and the other sending CC 85. I'll try to set this up and see if I can get it working.

[Rob]

I was able to accomplish what you are after by splitting a sustain pedal across 2 inputs. This actually begs for a feature request. If we think of an iO as having 4 input processors, with each input processor getting its data from an associated TRS jack, it should be relatively simple to specify which jack an input processor gets its signal from. For example, if we could specify that both inputs 1 and 2 should use the signal from TRS 1, it would allow this setup to work without needing the splitter. That would allow for some pretty powerful setups.

[manki]

Pretty cool idea indeed !

What got me asking is because upon reading the manual, i was under the impression that in order to transpose the MIDI notes to a certain value, a key input had to be made, so am i understanding right that you don't have to do key inputs for the transposition to take place ? you can simply set a permanent number to transpose to in the transformer and upon holding the switch (in unlatching mode) the transposition takes effect immediately ?

[Rob]

That method of transposing still works, but the MIDI Transformer can also be used. Here are the settings you would use for the transformer.

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And then one of the sustain pedal inputs, you would set it to control the On / Off state of the transformer. I've disabled pedal sensing and set the switch type to 'latching' even though my sustain pedal it momentary. This is to ensure good synchronization between the two input; the iO might otherwise get getting confused because the signal is split across two inputs.

image.png (34.55 KiB) Viewed 517 times

And here are the settings for the other input. This input is set to 'invert' so that we get 127 when the pedal is released. This actually depends on weather your switch is normally open or not.

image.png (42.63 KiB) Viewed 517 times

[manki]

Amazing !

My last concern is if the footswitch is released before the keyboard keys are, say while holding a chord down, the wrong note OFF messages would be sent when the chord is released as they would be sent now untransposed so i'm guessing the transposed notes would get stuck.

I had anticipated this problem and was gonna either code an IF statement with variables that keep track of it all or simply send an ALL NOTES OFF message upon pressing or releasing the switch, perhaps a third transformer effect would need to be applied for this to work with your device.

So yea if your 4x input MIDI Expression could be configured to stack all 4 transform effect in a single path in a future update that would certainly open up possibilities.

Sorry it's getting hard to explain all this (english isn't my first tongue), especially without context so i'll provide some optional context below just so it makes sense to whomever finds this.





--- OPTIONAL CONTEXT ---

The Prologue 8 is a 49 key - 8 voice synthesizer that can be configured to have two layers (two different timbres) with different panel settings for each one, they are referred to as SUB timbre and MAIN timbre each having 4 voices, all of it in the same patch.

Each layer sends its knob movements on different MIDI channels (say MAIN is CH 1 and SUB is CH 2).
In order to switch between which layer i'm controlling, i can press the hypothetical switch and send CC# 85, that's TIMBRE EDIT which selects what TIMBRE you want to be editing/performing its controls.

So far simple.

But here's the catch, each layer responds to key presses of the SAME MIDI channel (the MAIN one so CH 1 for both layers).
They get around that by having you decide which TIMBRE is played in which keyboard range (left and right, typical split point setup).

Consider that I want the MAIN timbre across all 4 octaves (whole keyboard range)
i press the footswitch to toggle TIMBRE EDIT to SUB -> the knobs now affect SUB alright
...but the keyboard is still palying the MAIN timbre,
that is unless i get across the chosen split point by pressing the octave button 4 times and that's slow...

Essentially what i'm trying to accomplish is to play the synth on the MAIN timbre on the whole keyboard range,
then at the press of a switch, BAM i'm now playing the SUB timbre across all keys and the knobs now respond to it as well.

Basically making it feel like i'm swapping synths when i hold a switch down.

[Rob]

My last concern is if the footswitch is released before the keyboard keys are, say while holding a chord down, the wrong note OFF messages would be sent when the chord is released as they would be sent now untransposed so i'm guessing the transposed notes would get stuck.

You won't get stuck notes. Note Off messages are always generated on the same channel / pitch that as their corresponding Note On messages.

[manki]

let's say i press and hold key C1
-> C1 note ON message goes synth midi OUT to device
-> device sends it back to synth's midi IN

C1 is sounding.

now i let go of C1
-> C1 note OFF message goes synth midi OUT to device
-> device sends it back to synth's midi IN
synth receives C1 NOTE off message and so
-> C1 stops sounding.

nothing fancy here.

--x

[now i press and hold the footswitch to enable +48 transposition]

let's say i press and hold key B1
-> B1 note ON message goes synth midi OUT to device
*[device transforms B1 to +48 and sends B5 instead]
-> B5 gets sent to the synth's midi IN

B5 is sounding.

[now i let go of the footswitch, notes aren't transposed anymore]

thereafter i let go of the B1 key
-> B1 note OFF message goes synth midi OUT to device
-> device sends it back to synth's midi IN (no transposition takes place)
Synth receives B1 NOTE off message

***B5 is still sounding because it never got a B5 note off message.


am i understanding this right ?

[Rob]

[now i press and hold the footswitch to enable +48 transposition]

let's say i press and hold key B1
-> B1 note ON message goes synth midi OUT to device
*[device transforms B1 to +48 and sends B5 instead]
-> B5 gets sent to the synth's midi IN

B5 is sounding.

[now i let go of the footswitch, notes aren't transposed anymore]

thereafter i let go of the B1 key
-> B1 note OFF message goes synth midi OUT to device
-> device sends it back to synth's midi IN (no transposition takes place)
Synth receives B1 NOTE off message

This is not correct. When you let go of the footswitch and then release B1, the MIDI Expression will send Note off B5 because the B1 was mapped to B5 when the note on message was generated. As I said, it remembers the channel and pitch of the Note on messages and uses that when it's sending the note off. The device remembers up to 24 simultaneous notes, so if you simultaneously played 25 notes, you could in theory trip it up).

[manki]

Brilliant ! i placed an order for the eDRUMin and will probably purchase the MIDI Expression in a few weeks... and another eDRUMin down the line, thank you