The LinkedBrainz project is primarily about mapping a relation database (the MusicBrainz DB) into RDF. The W3C RDB2RDF Working Group is focused on use cases just like this. The mission of the working group is to standardize a language for mapping relational data and relational database schemas into RDF and OWL. Richard Cyganiak recommended a video of the working group's recent panel discussion.
In the video, a nice blog post from Juan Sequeda is mentioned which reviews existing tools for mapping relational databases to RDF. There is also a survey paper (PDF) submitted as an input to the working group. These perhaps provide a nice starting point for a survey of tools that might be applied to the LinkedBrainz project.
It is very important that the LinkedBrainz project is aware of the work coming out of this W3C working group and adheres to the developing recommendations when possible. The intersection of Linked Data, SPARQL, and SQL is full of exciting developments and LinkedBrainz will hopefully emerge as an early success story.