Not the generic concept of TUI sequencers (i know, have used sequencers on c64), but any weird slightly different idea.

In my case i wanted flexible way to display lyrics, chords, strumming, metronome, fingerpicking, scales, chord shapes, etc, with an easy way for LLMs to define the backing-track, so a backing track DSL.

I think we'll see a lot of these very specialized software popping up, instead of generic solutions that contain everything and the kitchen-sink, where you don't use 90% of the functionality.