I want to use the spotify api to embed music into my service, however I'd like to add a high frequency signal (c 20khz) to the songs played. the signal would repeat and would not be audible to listeners.
I've read the Spotify API documentation, however it's written in such a way that really, only the author of the api would understand it :(. I can't tell if what I'm trying to do is supported.
Does anyone know?
The libspotify API just delivers you the raw PCM samples. You could mix in your high frequency signal before you send them to whatever you're using to play them, assuming that it's actually capable of reproducing your tone.