in music, is when one of the parts dwells on a note, while another part makes two or more lesser notes equivalent to it, by conjoint degrees.

Supposition is defined by a late author the using of two successive notes, of the same value as to time; the one whereof, being a discord, supposes the other a concord.

The harmony, Mr Malcolm observes, is always to be full on the accented parts of the bar or measure; but, on the unaccented, discords may transiently pass, without any offence to the ear. This transient use of discords, followed by concords, make what we, after the French, call supposition.

Concords by supposition are those where the continued bass adds or supposes a new sound below the fundamental bass; whence such concords always exceed the extent of the octave. Of these concords there are three sorts, all which are concords of the seventh: the first, when the added sound is a third below the fundamental sound; such is the concord of the ninth; and if the concord of the ninth is formed by the mediant, added below the sensible concord in the minor mode, then the concord is called the superfluous fifth. The second kind is, when the supposed sound is a fifth below the fundamental sound, as in the concord of the fourth or eleventh; and if the concord is sensible, and the tonic be supposed, this concord is called the superfluous seventh. The third kind is that where the supposed sound is below a concord of the diminished seventh: if it is a fifth below, i.e. if the supposed sound be the mediant, the concord is called the concord of the fourth and superfluous fifth; if it is a seventh below, i.e. if the supposed sound be the tonic, the concord is called the lesser sixth and superfluous seventh.