EDIT: I FOUND IT!!! It is called “Lonely to Organdy”. Finally!
so years ago I read a short and sweet BL (male x male) manga; it was a very short manga, maybe 6 to 10 chapters, black and white.
There was a boy who loved playing an instrument (probably violin if I remember correctly) but for some reason, he stopped. He was depressed and lonely but when he moved into his new apartment flat, he met a “ghost” boy who is supposedly dead, and he is the only one who can see and talk to the ghost. Over time he starts to play music for the ghost and gets encouraged to fight for his dreams again.
He gets very attached to the ghost too, there were R18 scenes of them being intimate, but as they became intimate the musician boy somehow got “tainted” so the ghost said they had to stop seeing/touching each other.
Overall it was a bittersweet story with a kind of a happy ending, I really remember the whole plot and scenes but not the name. I probably read it earlier than 2019, so it could be published anytime around 2014-2018, probably. Please send help if you know, it was so inspiring and I would really love to find it again!