I suggest you to consider using BuddyPress, which turns WordPress into a social networking site. You can have user types, media gallery, social interaction, etc.
I’d just install a forum and limit it to people looking for music or musicians and musicians looking for small gigs.
Let the musicians include their recordings or videos and encourage some talk of price and/or funding expectations.
Let the creative types show their videos needing jingles, intros, and background music.
I’d imagine very low prices on the musician side might get the ball rolling with the creative group responding with lower offers, trades of equipment, addon gigs, mentions, etc.
The people on both sides of that equation are bright and clever. Just establish a few rules, maybe a blacklist of banned words, and some anti-spam guidance. But loosen up where you can and let them show you what your site is about.
A site like that might draw some good advertisers after a bit.