I have just come across this thread for the first time, and have inadvertently found a work-round. However, I must point out that on occasion I get sounds cut off during state changes, which shouldn’t happen. Thankfully I practice a set list once I have made one, and learn where the unexpected cut-offs occur, and do a “work around”. This has relevance to the seamless song changes problem.
What I do to overcome the “potential silences” is to choreograph the song change. I use a FCB1010, and time when I jump on the song change pedal so that I enact the change t the end of one note, and complete the change with the next note. So if there is a silence, it is minimal, and maybe hardly noticed. Similar to So_Godly and Lovell, most of my live playing is in a worship band, and I have the advantage of the pianist being my lovely wife, Veronica, whoi s excellent at playing through from song to song, which disguises my momentary silences. Even so, the timed FCB1010 pedal press is very effective.
I am relatively recent to live playing, having suffered RSI for nearly 30 years, and on my return was told that for worship keyboard playing I would only need about 3 or 4 pad sounds. Although this is not true for me - I prefer to use whatever sound or voice will enhance what is being sung, and will have states for each verse, chorus, bridge, etc, and even multiples of these, the original advice does have relevance.
At the end of each song I can create a state which uses one of the alleged 4 pad sounds, and either “choreograph” the song change so the “inter-song” period is filled with a suitable pad sound. It might also be possible to start the next song with a state which uses the same pad sound!
An easier alternative is to set up a rack with said pad sounds, and put that into every song you set up. An advantage is that should the need arise to begin adlibbing, which is quite regular in worship music, an ubiquitous pad sound is always easily available, especially using something like the FCB1010.
Dave Dore has come up with another solution, which again I have been inadvertently using. A current trend in worship music is to combine songs in a mash-up, so all I would do is take the Cantabile song for each song involved and lump them all into one song, identified with “mash up” in the title. Effectively this becomes a “mother song” or “super song”, containing all the states from each of the songs involved, all in one file. This is particularly good if your set list doesn’t change much from gig to gig, but is a lot of extra work if your set list is different each time you play, as is the case for me. But if “Seamless” is important, it is worth the extra effort.
None of these are solutions, but are good work-rounds until a true seamless song change is available. Hope this helps, if only a little.