This works fine, unless it's at the very start of a song. Putting a LiveLoop trigger here causes Jamstix to go silent (it cycles through the bars, but the brain doesn't generate anything) and any subsequent triggers also fail to do anything. Ableton also seems to go a bit funny and hangs/crashes some time afterwards, although I can't be sure the two things are related (how would you tell
Due to the nature of Ableton, I need to put the MIDI message right at the start of the clip (it doesn't make any difference if it's a PC or a note message), otherwise Jamstix doesn't receive it early enough and changes part a bar late. However, a bit of experimentation shows that if the MIDI message starts fractionally late, Jamstix seems to work OK even if the trigger is at the very start of the song (ignoring the fact that it played one bar of the first part before switching to the one I actually wanted).
I had a similar problem with Jamstix 2 and never got to the bottom of it but I rather suspect it's the same thing.
I can send through a project that demonstrates the problem, do you need anything else?