You may or may not have noticed - during my Brave Fencer Musashi playthrough - that as I periodically visit the Allucaneet Castle, the background music seems to have a little extra...something, each time.
Depending on how many Musicians (including the Conductor) that you rescue - then go to speak to at the castle - the music will change to reflect the instruments respective to each particular musician.
I ran a second game alongside my first - here, I rescue all the musicians, then speak to each in turn so that you can listen to the changes, yourself.
0:00 - 1:07 - MusicianA (Musician Beef-Clef) - the default musician.
1:07 - 2:27 - MusicianB (Musician Pianissimeat) - adds a flute-tune.
2:27 - 3:43 - MusicianC (Musician Al Forte) - brings some drums and a neck-mounted metallic pan-flute to the mix.
3:43 - 5:46 - Conductor (Conductor Scores) - last but certainly not least, he brings in his violin.