Here's an explanation of John Coltrane's "Giant Steps."

https://www.youtube.com/watch?v=62tIvfP9A2w

The Coltrane changes are lovely, but if you slow them down they aren't substantially more difficult than other Jazz changes from that era. What makes Giant Steps so challenging is mainly the tempo.

Tommy Flanagan, the pianist who struggled a bit on the original Coltrane recording, put out a recording of Giant Steps with his own trio in the 1980s. Having had enough time by then to woodshed the changes, his improvs are exquisite. https://www.youtube.com/watch?v=O3PWynH-CEc