how to replicate it:
1) place a command block with a playsound command
(i used playsound random.explode @p ~ ~ ~ 100 0.6)
2)attached it to a fast redstone pulse
3)actívate the clock
4)deactivate the clock
5)wait for it to fully stop
6)re-enter the command block (doesnt matter if you change the command
7)press cancel or ok to get out the command block screen

if it was propperly made, when u do the 7th step you should hear the sound even if the command block is not powered

i dont know if it's just my client but i just want to share it

a screenshot for the replication: