Scratch

penlu wrote:

There's no way to play more than one note at a time but to make a few separate channels.  But the channels fall out of sync.  Is there any way to keep them together?

Hey penlu, in situation like this, you can try to use broadcasts to keep the channels in sync. I believe MyRedNeptune's Music Project uses this, so you can download it and take a look. 

penlu wrote:

I've been doing that measure by measure.  But this piece needs four channels-is there a better way?

Unfortunately, there really isn't a better way around this. You could try stretching it out to two or three measures and see if they'll stay in sync. If your project play notes on some kind of repeating beat, you could try to be a bit clever about it using repeat blocks and lists so you don't have to keep using so many note blocks and broadcast messages.

If the goal of making the project isn't about composing in Scratch, then an alternative option is to compose the project in outside program (such as Anvil Studio) and then import it into Scratch.