Awesome, my manski. Good for you (that's no small amount of beat-selling).
I am not an accountant or CPA, I can only tell you that A) you should talk to one, and B) a few things from my many years of experience being in the music business, and also being completely above board with all income, in regards to taxes...
* It would probably be a good idea to file some kind of paperwork to establish your company as a legit business entity, if you haven't done so already. Check out and get appropriate advice (CPA, attorney, etc.) on the various forms of businesses-- Sole Proprietorship, LLC, incorporation, S-corp, etc., and decide which one is right for you. If you're in the US, you'll have to deal with state and federal taxes, as well as some municipalities (like Yonkers), so having a business structure is an important step in legitimizing the deductions that you'll be taking.
* If you're asking about filing for this year, you might be a little late if you haven't been keeping track of your expenditures and getting receipts, etc., but for the future, you want to save receipts or invoices for anything that you spend to run, maintain, or grow your business. Again, a certified tax specialist will be able to give you more details, but you can take deductions for advertising (any business cards, Internet banner ads, flyers, paid networking sites, etc.), for business office expenses (any postage, website fees, copy paper...), and for any musical supplies (instruments, software, ) and equipment (computers, studio gear, etc.). There's a lot more, but it would be good to know more about how you operate your business, and again, best for you to seek professional guidance.
GJ