Playback going to multiple channels

I thought that I once read an answer describing why this happens, and what the fix is, but I can’t seem to locate it. Sorry if this constitutes a repost.

I’ve got a staff playing correctly on a single channel during editing, but during playback, it propagates to two channels. Why is Dorico doing this?

Here, you can see that the instrument is divided into three channels – one for a2, and two more for individual instruments:

Can you attach a little snippet of the project so I can take a look and see what might be going on?

Here ya go, Daniel:

channels.dorico (2.3 MB)

I think the main reason that this is happening is that you originally created a grand staff and then must have changed it to the trombone…That’s why is has staff (a) and staff (b). You need to create a new player or section and start again. In my experiments with this file there were some other strange playback issues as well (some notes not playing back) so maybe you should create a new project from scratch.

No, it has staves (a) and (b) because later in the score, I divide them into solo parts.

Let’s just wait and see what Daniel says.

Yes, absolutely!…I don’t think you can successfully use IRV and divisi on the same staff, but yes, let’s wait to see what Daniel says because this is very interesting.

Sorry, I’ve not had a chance to look at this yet, but I will do later today, all being well.

Problem solved by turning off IRV for that staff, then turning it back on again. So, the matter is merely academic now, although I’d still appreciate an explanation of what happened. I’d like to know what steps to avoid.

Sorry that it has taken me so long to look into this. Unfortunately I’ve not got a conclusive answer for you. The reason that two channels are playing back at the same time is because the independent voice playback data for the instrument has both the information for each of the three independent voices and the data for when independent voice playback is disabled. It’s not meant to: it should have either data for the three independent voices, or the data for the single endpoint when all voices are played back by the same endpoint.

I can’t work out how to get into that state, so I can’t offer you any "do"s and "don’t"s to help avoid this in future, I’m sorry to say.

Thank you sir, no worries.