Sustaining.

Sir Christopher Hogwood provides an analysis of what makes the following music masterpieces: Pachelbel's Canon, Purcell's Dido's Lament, and Fauré's Violin Sonata.

Memorability is sometimes achieved by the simple technique of repetition, in addition to more high-flown inspiration. Some of the simplest sustaining devices of great music are ground bass, ostinato or chaconne; this lecture shows that a canon can be more than simply "Three Blind Mice"...

The most important advice he provides about canons is how to stop them.