Any source soundOpen audio or video, record from the microphone or grab the sound that is playing: on the phone through Android's “Share screen” dialog and, on the computer, the sound of one of the PC's outputs (your headphones, for example).
Trim and fine-tuneSelection with a cursor, pause and zoom on the waveform; fade in and out, volume with normalize, mono or stereo and MP3 quality. You hear the result live, with the filters.
Save where you wantOn the phone it exports to the Ringtones folder, so it shows up straight away in the ringtone list, with “Set as phone ringtone”. On the computer you save to the folder you choose. It never replaces a file with the same name.
No network, no dataEverything is done on the device itself: the Android app doesn't even have Internet permission and the Windows version only talks to the computer itself. On Android it asks for the microphone, notifications (recording notice) and, only when setting the ringtone, to change system settings.