I do this all the time with Cantabile (most of my “songs” are actually sets of up to 16 songs, each of which overlaps the next), and I find that Cantabile is excellent at this as long as you do what @Sausagefingers describes:
- Each of my “songs” is actually a linked rack in Cantabile.
- A “set” is actually a song in Cantabile, with one song state for each song in the set.
- Each song state has the MIDI route to the relevant song rack enabled, and all the other routes disabled (except that I have always-enabled routes for foot pedals to all the song-racks, so that foot pedal events are never blocked).
- Switching song-states changes songs. This works perfectly because Cantabile still sends note-off events along disabled MIDI routes; it only blocks new note-on events to disabled MIDI routes. So I can sustain the chord of the previous song with my fingers or with the foot pedal, switch to the new song, start playing, and everything works just as it should.
- If computing resources are a problem, I disable all racks except the ones for the current and previous songs in each song-state. I can even create a delayed binding that disables the previous rack after a set length of time if necessary, so that only one rack is enabled most of the time.
- I only need to create this special song once. New song sets can then be implemented by just replacing the racks in the song to quickly create a new song-set.
Once upon a time I trialed Gig Performer vs. Cantabile and concluded that Cantabile is vastly superior in terms of power for this. Gig Performer seems easier and mostly equivalent until you dig into it and discover that it has far fewer options relative to Cantabile when you get down into the details. This makes Cantabile a little harder to learn, but once learned it offers far more power.