Mental song jamming

I was working on Neil Young's "After the Gold Rush" and then Ru-Jun asked me to play "Sundown", which I haven't played in a while. The first line of the verse is similar to "After the Gold Rush", so I couldn't do "Sundown" without listening to it. As a solo performer, it's sometimes hard to get a song clearly into my head enough to start playing it. This happens more often with particular songs than with others.