What you, or whosoever, needs to do to get this effort off the ground, is first to put together a catalog of appropriate recordings that you, or the artists, control all the rights to, and that you, or someone who is readily available for endless meetings, is intimately familiar with.

Then you, or that special someone, have to avail yourselves to producers, directors, and writers with suggestions as to what piece of music will fit where in which project.

Then, when it comes down to it, you or whosis will have to deal with things like, "We need a tune for the climax where the hero says "happy birthday" in Esperanto and dies", and things like, "The scene is thirteen seconds, the sound clip is twenty seconds, and Dave Swarbrick is
singing in the place that the hero says "happy birthday".

And you need complete control of the rights so that no one ever says, "We can't release the film because control of the song at the end belonged to some guy who died and left all the recording rights to his pets".