For it's mainly how familiar I am with the music. I have a playlist that I've listened to hundreds of times so regardless of the style it doesn't become distracting. It all becomes 'as ignorable as it is interesting', as Brian Eno said ambient music should be.

The deeper the concentration, the fewer words I want - or at least words I understand. Classical music with words I don't understand can also work quite well. There also seems to be a vague point where I have heard the lyrics so many times they stop being distracting.

Funny. For me, instrumental music is just as distracting. If I don’t know the music I listen to well enough, my attention will go there and make any coding or reading impossible.

Yup this. While working I love instrumental-only electronic music: no voices.