How will be establishing price for track? Will be same price for all of them or will be registered by artist?
The price for every track is up to artists theirself. They have right to decide its price.
Price for track on platform be in OPT or will be used fiat money? I means if i want to buy a track first of all i need buy opt or i may pay in usd?
The price for every track will be in OPT, however the team will integrate payment processor before mainstream release.
How will an artist apply his/her song in the library? Is it going to be free?
Do you mean to sell their song? Once they purchased the decryption keys, yeah it's free and they have right to decide the price of their song.
another interesting question: imagine that i'm an anonymous underground artist who is popular in the definite community, so opus users willingly buy my tracks, and there is a question: how will the taxation procedure be integrated into these particular market relations between an artist and the platform?