Know in anime/manga that's 音乐 theme?

While I've never seen it myself, I've heard BECK: Mongolian Chop Squad is pretty good. Also, I never finished it, but NANA seemed good as well. That's all I can think 你 that 你 haven't named. ^-^

天使 Beats! features this all-female rock band called Girls Dead Monster

::Inhales deeply::

*Fancy Lala.
*Perfect Blue. (partly).
*Kodomo no Omocha (Partly & comically bad).
*Idol Densetsu Eriko.
*Suite PreCure.
*Tari Tari.
*Wandaba Style.
*Mermaid Melody Pichi Pichi Pitch.
*AKB0048.
*Pretty Rhythm.
*Wake Up, Girls!
*Lovely Idol.
*Violenist of Hamelin.
*Skip Beat.
*Symphogear.
*Pyu to Fuku Jaguar.
*Princess Tutu.
*Anything to do with Macross & Robotech.
*Nodame Cantibile.
*Interstella 5555: The 5tory of the 5ecret 5tar 5ystem.
*Miss Monochrome.
*Kids on the Slope.
*Shindo.
*Love Live.
*Gauche the Cellist.
*Aikatsu.
*Detroit Metal City.
*Black Heaven.
*Shinkyoku Soukai Polyphonica.
*Change Pop Metal Session.
*Nerima Daikon Brothers.
*Super Sonico.
*Lemon 天使 Project.
*Beck.
*VS.
*K-On.
*Aishite Knight.
*Voiceful.
*Nana.
*Full Moon wo Sagashite (Not to be confused with Full Moon ni Sasayaite).
*La Corda D'Oro.
*Solanin.
*Kanon.
*Beck..
*Sensual Phrase.

Possibly Lucky*Star & Suzumiya Haruhi no Yuutsu...I never could get past 更多 than a few episodes.

Boys 爱情 或者 矢追 genre:
*Gravitation.
*Zetsuai/Bronze.
*Fujimi Orchestra.

Okey! Have fun!

Your Lie in April is fairly 音乐 themed. But its sad af.