I came to file the 'changing gamemode causes music to stop' bug, and see that hundreds of people have already filed the same bug. It is resolved as 'working as intended', as I guess there is some music that only plays in creative mode or whatever.

This is a broken design. People change gamemodes all the time. Many maps with command blocks change players gamemodes. I change gamemodes when map-making. I change gamemodes when filming LPs for flying and cinematics. Spectator mode makes more reasons to change gamemodes. It is ridiculous to have the music just 'stop' because someone happens to do some unrelated action in the game. Your customers agree with me (look at all the duplicate bugs).

At the very least, if an existing track is playing, let it keep playing until completion before switching to the new gamemode-set-of-music-tracks.

It is so frustrating. At first I would consciously make effort not to change gamemode if music I liked was playing. But I would still accidentally change it sometimes. Finally it was so bothersome that I turned off the in-game music, bought C418's soundtrack, and manually play it while playing the game. The in-game music is great. It is ridiculous that I have to spend so much effort just to listen to it while playing the game.

If this design is technically difficult or expensive to change, then fine, leave this bug open as unresolved. But don't just resolve it as a duplicate or 'working as intended', because clearly no one likes the way it works.