Bocchi the Rock, Girls Band Cry, and other girls' band shows seem to be all the rage.
But the work you could call the origin of it all is K-ON!!

Yui Hirasawa, who failed at everything and couldn't even decide on a club from the moment she entered high school, was told, "This is how you end up a NEET, isn't it?" Steeling herself, she joined a band, and that turned out to be the Light Music Club. There, she was talked into joining by the three others, bassist Mio Akiyama, drummer Ritsu Tainaka, and keyboardist Tsumugi Kotobuki (because the club would be disbanded without four members). Reluctantly joining, she awakens as guitarist and vocalist over the course of many an after-school tea time. That's the story.

It's more of a slice-of-life anime, where nothing especially dramatic happens and you simply enjoy the gentle, easygoing atmosphere of daily life and the girls' chatter. It was serialized in Manga Time Kirara. It was so wildly popular that, after the main story ended, two spin-off serializations followed: a college arc set after the girls graduated, and a junior arc depicting the Light Music Club after Yui and the others had left.

The anime adaptation was handled by Kyoto Animation, renowned for its artwork, directed by Naoko Yamada, with series composition by Reiko Yoshida.
Director Naoko Yamada went on to work on "Tamako Market," "Tamako Love Story," and "A Silent Voice," then left Kyoto Animation and worked on "The Heike Story."
Reiko Yoshida has put out all sorts of works, among them "Violet Evergarden" and "The Heike Story."
Jukki Hanada also participated in the scripts, and he would later take part in numerous Kyoto Animation works such as Love, Chunibyo & Other Delusions, Beyond the Boundary, and Sound! Euphonium. Outside of KyoAni, his credits include Love Live!


The girls' band name in the show is "After School Tea Time." There's also an album that compiles all of After School Tea Time's songs, and after agonizing over which to introduce, I decided to go with this original soundtrack.

The composer is Hajime Hyakkoku. Originally a composer, he provides songs to all sorts of artists. He worked on various character songs for K-ON! too, and he also arranged "Tsubasa wo Kudasai," which plays in the first episode, as well as the still-rough Light Music Club's performance from before they were named as a band.

Let's listen to the music in question.
First, "One? More? Tea?" which plays in various spots like the next-episode previews.
It has a thoroughly slice-of-life feel and a finish that warms the heart.

https://www.youtube.com/watch?v=ltDmFTC-cpQ


Next up is... is this an insert song?
I didn't recall it, so I looked it up and found it's "Amefuri," used in episode 5 of season 2.
It's a surprising track that, despite being Original Soundtrack I, was prepared even for the second season's material.

https://www.youtube.com/watch?v=NHCLTlkmywk


The last one I'll introduce is another phantom track that wasn't used in season 1.
"Usagi to Kame" (The Tortoise and the Hare). Yui Hirasawa is singing, but she comes across as either really childlike or really like a granny.
Looking this one up too, I found it wasn't used in season 1 and was apparently used in episode 7 of season 2.

https://www.youtube.com/watch?v=lZ2_TVK-9c0

Bocchi the Rock is a work in the Manga Time Kirara lineage, but without K-ON!'s success, it surely wouldn't have been such a hit.
And it's not just K-ON!. I think BanG Dream! and Girls Band Cry wouldn't have existed either.
It's no exaggeration to say K-ON! created the girls' band genre.
It's not too late to start now. If you haven't watched it yet, please do give it a watch sometime.