Add a link to the topic to your forum signature.
Post a link to the topic on the Songstuff Facebook page wall.
Check the boards using advanced search for topics that over lap with yours. Post a reply and include a link to your topic. Even replying to an old topic can pull in members who are currently inactive as they might receive notifications. You could also send people who replied to that original topic a PM.
Search our community profiles and blogs using advanced search, yet again PM members who have shown interest in the topic before.
Ask members in your topic (edit your first post) to like your post using the tick box, and share a link to the topic on their social media sites. Just explain your passion for the topic and that you would appreciate them doing whatever they can to spread the word.
You could also post links to the topic in other websites assuming they permit the posting of such links. This could be as simple as tweeting it or sharing on FB, to music forums that allow it.
Hopefully that gives you some ideas to go on with