This being John Martyn in the 70s, he was probably half out of his mind on who knows what cocktail of drugs and booze at the time, too. Maybe not this late in the 70s but probably.

Anyhow, it's all about the hammer-ons and pull-offs with this kind of playing.

To be fair, the whole beginning monologue is him explaining that he wrote it entirely as a gimmick to make fun of the way audiences fetishized technical playing in the 60s UK coffeehouse scene. The whole piece was originally him mocking his audience so subtly that they didn't get it, and yet it's also a really good piece of music on its own.

So yeah, big gimmick.

There's a great story his wife told in an interview about Nick Drake (who was one of the only musicians he was friends with) bringing a Tim Buckley record over for John to hear, and after maybe a minute John kind of furrowed his brow and said "too many octaves" and took the record off. He was pretty notorious for not thinking too highly of his peers, even more so than Robbie Basho.

Also this:

https://www.youtube.com/watch?v=T-CkvEcdubU