You can find trending music clips to use as ringtones on sites like Zedge's Hot Song section . Common Ringtone Issues

While MicroSIP doesn't have an internal "story" mode or a built-in storefront for ringtones, you can easily customize its ringer by replacing the default audio file in your system. Customizing MicroSIP Ringtones

: If you are looking for a technical "paper" or documentation on audio handling, MicroSIP is built on the PJSIP stack, which handles the signaling for ringtone alerts via the INVITE and 180 Ringing SIP messages. MicroSIP online help

: You can configure MicroSIP to play a short tone and pop up when a call is automatically accepted.