I've been trying to figure out the same thing and I get different answers from different people. Even two people at the tax-institution had different opinions.
I don't do mastering so this is for my production and mixing work aswell as for songwriting royalties and producer's royalties.
The VAT % for the above mentioned is different within my country (Sweden), 25% for productions and mixes, 6% for royalties and I can imagine that it's wildly different from country to country.
However the general opinion here seems to be that if my company has a valid VAT-number registered in the EU and the customer has one aswell, then VAT is 0%, within the European Union. For other parts of the world I take it case-by-case.
It worries me though, since I don't want all of a sudden to be forced to pay a lot of VAT that I never charged from my customers in the first place...