K-On!, Tenshi no 3P! Recommendations
Bunch of cute girls decides to start light music band.
Lots of cuteness and moe.
Main difference is that Tenshi no 3P! actually has a male lead, thus is a harem, while K-ON! is clasicall "Cute Girls Doing Cute Things" with only girls.
Anyway, if you enjoyed one, you will most likely enjoy another.