Here is an excerpt from the most recent biography of Gould, Kevin Bazzana's "Wondrous, Strange." The context is a discussion of Gould's early training under his teacher, Alberto Guerrero.
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"The most curious of the exercises was 'tapping,' which helped to develop what Ortmann had called 'pure finger-technique' and enhance the ease, evenness, and clarity of touch. As Beckwith described it, tapping 'consisted of playing the music for each hand separately, very slowly, but making the sound by tapping each finger with the non-playing hand. One learned from this how very precise and economical the muscle-movements needed for fast playing really could be.' (The fingers being tapped are placed in the correct position at the keyboard, resting on but not depressing the keys, and the fingers are tapped at the tips.) This would be followed by slow, staccato practice before the piece was brought up to tempo. As a result, the brain learned what was required in order to play in a relaxed manner with the fingers alone doing the work.
According to Dudley, Gould 'had been tapping everything' under Guerrero, and Gould admitted that, when making his famouis 1955 recording the Goldberg Variations, he tapped each variation before recording it - a rpcocess that took altogether about thirty-two hours. "
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Walter Ramsey