Multiple sounds on one instrument, playback oddity

I’d like to be able to change playback sounds mid-piece without assigning multiple instruments to a single player. In this example I have a guitarist, and I want their sound to change from clean to distorted.

I found a good solution here

The clean parts are notated in up-stem voice 1, the distorted in up-stem voice 2, and I’ve done the necessary tinkering (I think) in Play mode so that those voices are assigned to different playback sounds.

The sound does change, but there’s also this big long low note at the very beginning of the passage which isn’t present in any voice. I had this happen in a project I’d imported via xml but I was able to replicate the same issue in a brand new test file.

What am I missing, or is this is bad solution to what I’m trying to accomplish for some reason?

I have a short example file I can attach if permitted! Cheers.

The low note is a keyswitch which your Expression Map is not filtering out, so you hear it.

It means you have an incompatible Expression Map for your instrument sound. You need to find (or create) and apply the correct Expression Map in Play mode.

Okay! Thanks.

I googled expression maps stuff, but I’m still not sure how to tell what expression map a given player or instrument is using, or what I would have to change about an expression map to avoid this issue…

Instead I changed the instrument sound from General Midi guitars to one of the HALion ones I think, and the issue seems to have gone away.

Is there a single expression map I should use for any and all GM instruments or is it less simple than that?

You can see which expression map is used for each instrument in the Endpoint Setup dialog. There’s no default expression map included with Dorico that will allow you to switch between e.g. clean and distorted guitar.

You would likely have to change the Player form one voice or instrument to the pother and assign any second voice to a separate MIDI channel (slot) where you can apply a separate expression map (if changing the instrument itself didn’t let you change the sound.)