The Perfect Musical Symmetry of Avatar the Last Airbender

From Sideways.

Long ago, all the leitmotifs lived together in harmony
Then everything changed when the fire nation attacked


Sources and other great links:

Theodore Morris’s video

A list of leitmotifs in AtLA

Diegetic music of AtLA

An analysis of AtLA’s music

A reddit post listing off leitmotifs

Another thread just talking about how great AtLA’s ost is

Interview with the track team discussing some of their choices for the music

Another interview with the track team talking about the music

Another blog post going over AtLA’s music

And honestly, tvtropes had a few things to look out for, worth looking at if you want an easy place to start