This is rare type of shounen manga.
Sorry, maybe reality too much and hurting my eyes; all I can see is ecchi, harem, incest and isekai everywhere.
This is better than everyone's Your lie in April. When I don't really like that series, Kono Oto Tomare shows different sights of music from shounen perspectives. And it's obviously rare, it is different with seinen/josei like Piano no Mushi or Nodame Cantabile who shows deep approachment in every single steps of it.
Another series which similar to this Mahiro no Oto. I really recommend it, but you should read the raw because it got abandoned for more than 5 years.