Karma is a kind of song that is pretty difficult to say too much about. I play all the instruments, mostly improvised.
I usually record three drum takes, with different ideas and grooves. Then I choose the one that I like the most. Guitar is always one take, but I often record several guitars with different amplifiers etc, where I try different things. Bass instruments are usually two different takes, one for each of the two best drum takes.
The trick is to get all the instruments to respond to each other, even though you can only play one instrument at a time. I need to mentally play all the key instruments in my head, so that all the fills and quirks complement each other after the recording
I give myself some time to mentally prepare for this. And I totally avoid playing any instruments at that stage, and kind of meditate on the song instead. This can take days, weeks or hours, but I know when I am ready. The recording itself seldom exceeds two hours (including all key instruments)
Even though it would be nice to be warm on the instrument I'm about to play, I feel that it creates borders, and limits the song. If I were to focus on a specific instrument, it easily creates bad habits, almost like a handicap. Its the whole piece together that is the instrument. Everything has to fit subconsciously, instinctively.
This approach works for songs like Karma, but not on all songs, usually it is a combination of things.
Anyway, in my experience a song never stands still, and song is never finished. Music is motion.