I made a nice song with note blocks, started the recording with /supplementaries record start, stopped it with the stop command, pulled out my flute, and played the song at a crazy fast tempo! It was hilarious, but not at all what I was expecting.

Edit: Here's a recording of the song and the flute version: https://medal.tv/games/minecraft/clips/uqPJtF3Fbz3yT/d1337ZXr8iVi?invite=cr-MSxMYzQsODYyMzA1NTUs

Hm that shouldnt happen. I think the command had an extra parameter for tempo. If not you can edit it in the JSON it generated to slow it down

Can also vouch for this issue, it happens when you test the playback or use /reload
it resolves if you leave and join

Fixed