You are correct that music isn’t able to have a new time signature within a bar. I forgot about that after taking nearly 10 years of piano myself. I got caught up in the technical side of things when moving my signatures around on my track and didn’t think about it.
So, I suppose I will have to figure out the time signatures of the different sections, huh? For example, the opening section of my song has a 3/2 time signature (8 bars). Then, the second part of the song has a 4/4 time (8 bars). The third part has a 5/4 time (4 bars). Everything is dandy with setting up my signatures for these sections.
The problem I face is when I come to these sections later in the song. This time around, I’ve extended or shortened some of the sections. For example, in the beginning of the song, I played the 3/2 section for 8 bars. The next time around, I want to play it for 8 1/2 bars. How do I calculate the time signature for that new section?