I've started playing around with the tracker to add some basic music / jingles but I've noticed that in some situations notes are being skipped. For examples I have a simple 5 note chime that plays perfectly in PAL, but in NTSC, or if I have a longer instrument, or if I add a second channel it starts dropping notes. I'll keep playing around with it to see what I can find.
There's only 2 voices, so if they're both currently occupied, then either the new sound or one of the currently playing sounds has to be dropped... you can tweak the sound priority in the instrument definitions to make the compromise you prefer. In this case it sounds like you should lower the chime instrument priority, so it can be interrupted sooner. (the driver decreases the priority of any playing sound over time, exactly to avoid a long playing sound doesn't hog the channel, unless you override that by setting the priority to a large value.)
In the case of the Salvo theme, drums have priority=0 (only playing when there's a free channel, and giving up the channel to any new sound), and other instruments have varying priority. Arpeggios use an instrument with very low priority too, because you'd never notice some of those notes drop out, when the melody is playing over top.
It's also useful to use syncopation in your compositions, since that can avoid the melody and harmony competing for the same beat. There's a similar tip for making arpeggios that play a rest as the first note in the TIA Apreggio Tips doc.