Maybe could use autocomplete field on the Addition of New Release form for genre? So then user doesn't always have to manually type in the genre. This could of course be overriden with any non-predefined genre tag. Would mean less typing for releaser, and less error-prone submissions.

Any example?

Planned autocomplete on artists fields but how to suggest genre.., complex genres?

...complex genres?
Как группы на сплитах, только добавлять слэш мжду ними?

The best example I can give is in the Mp3tag program. The main problem with autocomplete is that it will only return 1 result at a time.