I’ve calculated what are possible crystals that could be used in audio applications with the rp2040. The premise is to be able to generate i2s MCK, BCK and LRCK while also produce exact 48MHz USB clock. The two best crystals I came up with in the range valid for the rp2040 (between 5MHz and 15MHz) are 9.216MHz and 12.288MHz. These two crystal frequencies seem to be widely available too. Analysis was based on audio sampling frequency of 44100Hz. Results for other audio frequencies are provided but there might be crystals that are better suited for those.