(Gk.: ‘raising’, ‘lowering’).
In measured music, the terms used respectively for unstressed and stressed beats or other equidistant subdivisions of the bar. Originally they referred to raising and lowering the foot in ancient Greek dance. Later they were applied to the unaccented and accented parts of a poetic foot, and hence acquired their association with weak and strong beats. For music since the 17th century they mean much the same as, respectively, Upbeat (or Off-beat) and Downbeat; the directions ‘up’ and ‘down’ remain associated with them by their respective functions in conducting.
In 1558 Zarlino coined the expression fuga per arsin et thesin to refer to imitative counterpoint in which the answering voice inverted the theme stated by the leading voice. Although this is in reality a misapplication of the original Greek terms, most musicians of the late Renaissance and Baroque who were familiar with Zarlino’s work, including Morley and J.G. Walther, accepted the association with imitation by inversion. Marpurg (Abhandlung von der Fuge, 1753–4) reconciled the two conflicting traditions by redefining ‘per arsin et thesin’ to refer to the entrance of a theme (usually a fugue subject) with displaced accents, former strong beats becoming weak and vice versa. Entries in Stretto (see Stretto (i)) may well be ‘per arsin et thesin’ but are not usually referred to as such because the ‘strong’ and ‘weak’ beats of the subject are superimposed. Displacement of the subject by half a bar in 4/4 time, common in Baroque fugue, does not constitute an example of the device.
PAUL WALKER