What is similar? Does it need to be a band anime? Does it require social anxiety characters? Just cute girls doing cute things (CGDCT) in general? Have yuri elements?
slice of life (SOL) with characters playing in a band: K-ON! (band aspect is secondary)
SOL with anxious main character: Hitori Bocchi no Marumaru Seikatsu
general SOL/CGDCT classics: Lucky Star, Nichijou, Azumanga Daioh
more modern SOL/CGDCT: Kiniro Mosaic, Gochuumon wa Usagi desuka?
SOL with yuri: Hidamari Sketch (moderate, also a classic), Yuyushiki (lots)
edit: I personally don't think that Bocchi the Rock! is super laid back, but if you compare it to action shows it obviously is. If you really want to go the laid back route you can look into the genre Iyashikei ("healing type") with anime such as Non Non Biyori, Yuru Camp (still have to watch this one so can't verify personally but is very popular) and Yokohama Kaidaishi Kikou (absolute classic).
You are probably referring to Danshi Koukousei no Nichijou. There are a lot of SOL anime so I got to choose something. Personally I think it is pretty good but not as good as some other anime that I would recommend over it. As well as the fact that Bocchi the Rock has a mostly female cast so I unconsciously selected anime that are similar in that regard. If OP wants to try something with a large male cast this is the only anime I can think of that would be fitting so it's good that you mention it.