The analogy with music is interesting. Superficially, the musical activity which looks most like typing is simply playing an instrument. And sight-reading does feel a bit like typing. But I wonder if he's talking about transcription in that quote. One can sight read complex music without learning anything about it if they happen to just be a good sight reader. But transcription really does force you to pay attention to structural nuances you otherwise wouldn't get just by listening to a piece of music.