Answer:
serial; parallel
Step-by-step explanation:
Serial and parallel processing are the two processing mechanisms. In serial processing one, abstract or object is processed at a particular time. In parallel processing, more than one or many objects are processed at one particular time. This process continues simultaneously.
As per the given excerpt. the scales that the child is practicing are comparable to serial processing. At the same time, the chords that the child is learning is comparable to parallel processing.