&gt;<i>The examples given for sports training seem practical, but I&#x27;m having trouble envisioning small variations of a similar type for things like instruments. Maybe varying the size&#x2F;weight of the piano keys, or fret spacing on a guitar?</i><p>Huh? It&#x27;s not about changing the instrument. They mean stuff like practicing in different tempos, the same pattern in different scales, playing a piece with different accompaniment styles, playing the piece with open vs barre chords, or with a different strumming pattern, etc.