i'm writing a book where the protagonist is a musician, it's a novel, and in those books I think of drawing a scene where his passion is listening to him. What's the best way to insert a scene like this?
You do not make it clear whether your struggle is with the formatting of the lyrics (a question which @Cyn answers) or with structuring the scene, a question which I will attempt to tackle.
The Lord of the Rings is chock-full of characters bursting into song at every opportunity. Tolkien sets up the scene each time, but as for describing the actual singing, he gives the singer little more than a dialogue tag: "he began not to speak but to chant softly" (LotR I, chapter 11 - A Knife in the Dark). "a single voice rose in song" (LotR II, chapter 1 - Many Meetings). Tolkien's poetry stands on its own, because it's good poetry. It produces an effect in the reader. The reader is affected just as the listening hobbits are, so describing the effect on the characters is redundant.
But what if you don't have your own lyrics, whether because you can't write poetry (a question I asked a while ago), or because your character is singing something famous in real-life? In that case, you go and describe the singing and/or the listener's impression of the song.
Here's an example, from Diana Wynne Jones's Cart and Cwidder, chapter 1:
They were strange, moody little songs, with odd rhythms. Dagner made them even odder, by singing now loud, now soft, for no real reason, unless it was nerves. And they had a haunting something. The tunes stuck in your head and you hummed them when you thought you had long forgotten them.
Write up the lyrics in the usual poetic style (with line breaks and also stanza breaks). Insert in the text by starting a new paragraph then indenting the lyrics on both ends. In a published book you might italicize or change the font, but don't worry about that in your copy.
If the lyrics are just a short line, you can insert it directly into your text and use quote marks around it. Or italicize.