Can a musician claim everything in the studio plus the studio room in his house under his taxes if so how to go about that

It depends on what is in his studio and if the room is used exclusively and regularly for business. 

If your room is used Regularly and exclusively for business, then you would be able to claim this room under the home office deduction.  In order to claim the home office deduction, you must have a profit.  The home office cannot be used to create a loss.

As for the items in the studio.  If they are used for your business then yes, you would be able to claim them for the business. Some items, may be expensed, while other items may need to be listed as an asset.  For example, if you bought a $10,000 sound system, that would need to be listed as an asset to be depreciated.  When going through the assets that are depreciable, you may be able to claim the Section 179 deduction.  If you bought drumsticks that cost $100, you would be able to just list them as an expense.  

Reporting Self-Employment Business Income and Deductions