You paid for the studio, the engineer, the musicians, and the vocalists—so now you own the finished recording, and have the right to license it for inclusion in TV and films—right? Not necessarily.
If you recorded the song in your home studio, played or programmed all the instruments, and sang the vocals, you clearly have the right to license your recording. But … if you hire a singer and/or musicians, you can only use their recorded performances in TV shows or films if they have granted you permission to do so. If you hire someone to produce your recording—or use a demo service to fulfill that function—you’ll need their permission as well.
The solution is to have all musicians, vocalists, and producers sign a work for hire agreement—a document that you and the performers sign, stating that in exchange for payment, you own all rights to the performance—including the right to license the recording for television and film, and that the performer is not entitled to any additional compensation. This agreement is sometimes called a musicians’ or vocalists’ waiver. As an incentive, you might consider offering to pay your vocalist a percentage of any income you earn from master use licensing. Note that if you record demos in Nashville with musicians and/or vocalists who are members of their respective unions—they are not permitted to sign a waiver or a work for hire agreement. Your option is to upgrade their payment according to the rules prescribed by their union.