Guys...

http://www.mangago.zone/read-manga/yoru_to_asa_no_uta/

http://www.mangago.zone/read-manga/star_right/

http://www.mangago.zone/read-manga/kreuz/

http://www.mangago.zone/read-manga/piano_no_mori/
(Dabest!!!!)

http://www.mangago.zone/read-manga/shigatsu_wa_kimi_no_uso/
(Heartbreaking huhu. You should definitely watch the anime vrs! Beautiful piano pieces and stunning animation)

http://www.mangago.zone/read-manga/soul_catchers/
(Interesting and funny concept about orchestra hehe)

http://www.mangago.zone/read-manga/fukumenkei_noise/
(Adorable)

http://www.mangago.zone/read-manga/beck/
(Seriously dabest!!!! I felt so helpless after I finished the manga. You should try searching for beck's songs in youtube/ watch the anime. You will not regret it!!)

And many more~
Try checking out the music tag
http://www.mangago.zone/tag/Music/

http://www.mangago.zone/read-manga/beck/ I agree. This manga is the best in the music category by far, and it's one of my favorite manga period.
http://www.mangago.zone/read-manga/wood_stock/
http://www.mangago.zone/read-manga/nana/
http://www.mangago.zone/read-manga/shiori_experience_jimi_na_watashi_to_hen_na_oji_san/
http://www.mangago.zone/read-manga/bremen/
http://www.mangago.zone/read-manga/teen_spirit/
http://www.mangago.zone/read-manga/given/

Thank you everyone for the suggestions!!! Much appreciated..!