Third Sanctuary from Deltarune by Toby Fox.

There's a lot of emotional investment in that song at the moment. And the ringtone is just the very first riff on repeat, as that part sounds like an actual ringtone (wondering if that's on purpose)

This song is famous for having an absolutely insane time signature that somehow works, as shown in this visualizer: https://m.youtube.com/watch?v=De0FDShxgrs