How do you run a command after some playsound music?

You can create an structure like that:

And when music start to sound execute /time set command substracting 20 to 22340 by each seconds you want to delay the command.

For example:

• If music duration is 10 seconds you must delay the command by 10 seconds so:

  22340-(10*20) = 22140

  So you must execute /time set 22140 when music starts sound

• If music duration is 17 seconds you must delay the command by 17 seconds so:

  22340-(17*20) = 22000

  So you must execute /time set 22000 when music starts to sound

I hope I've explained that clearly

You could have a dispenser with arrows in it pointing towards a wooden button and when the music starts trigger the dispenser. The arrow will despawn in 60 seconds (1 minute). For example, (I did this very same contraption) I played records.11 and triggered the dispenser, shot one arrow, and afterward I had a line of repeaters (4 tick) that triggered a tp command in the end.