We currently don't sign with artists individually, only record labels and publishers (both indie and major labels). If you have a record label/publisher please send us the contact details to firstname.lastname@example.org and we'll contact them when appropriate.
If your tracks are self released, email email@example.com with all the publishing and release info for your track. Even if we generally don't sign artists/songs individually, you're welcome to contact us with all the details and we'll get back to you as soon as possible.
To be able to add your tracks to our library, it has to be an original recording (without any samples in it) which you have all the publishing rights for.