This branch of scientific composition ought properly to be called the preparatory school of the fugue. The rules to be observed are very much less strict than those applied to the real fugue or canon. It is indeed only necessary to take a theme, or subject, in one or perhaps two of the parts, and to imitate it in another part, as may be most convenient. The distance of the intervals taken, by ascent or descent, as also the regularity of the progressions and the correct involution of the parts, need not be so carefully considered; it is also permissible to combine with the leading subject other analogous ideas. For these reasons imitation is an artifice very available in the florid style of composition, on account of its efficient aid in carrying out a subject in a workmanlike manner, and giving an air of unity to the whole piece by means of the similarity which one leading idea is made to bear to another. Imitation is a sort of graceful counterfeit of the fugue, and, if cleverly used, makes no bad substitute for it.

A partial or periodic imitation may be used upon any selection of intervals, as will be seen by the following examples.