Arsis

What it means

Arsis and thesis denote the pair of lift and fall out of which the rhythmic course is built. The terms come from ancient prosody and were taken over from there into music theory. Arsis means the lighter, leading-toward half, thesis the heavier, aiming one — in today’s language roughly the relation of upbeat and accented beat.

The assignment is not uniform in the transmission. Whoever meets the term in the literature should therefore check in which sense the particular author uses it.

Musical use

The idea behind it is more fundamental than the terminology: music runs not as a chain of equally weighted events but in motions from one point to another. Notes lead toward or fade away; a phrase has a goal. In medieval and early-modern music theory the pair of terms was bound to the beating motion of the tactus, in which the fall and the rise of the hand together formed a unit. In the chant scholarship of the nineteenth and twentieth centuries it played a role again, when the question was how the performance of liturgical chant was to be articulated — there too the terms are not uniformly used.

The meaning of arsis and thesis has been reversed in the course of history. In Greek rhythmic theory arsis denoted the raising of the foot in walking or dancing, that is the light part, thesis the setting-down, the heavy part; Bacchius still describes it so in the fourth century AD. Roman grammarians such as Marius Victorinus also referred the words to the raising of the voice, and in prosody arsis has since often meant the stressed part. In music theory, by contrast, the original meaning holds: arsis is the upbeat, the light time. Because of this contradiction the classicist Martin West recommended avoiding the terms in metrics.

Performance practice

When practising, think in goals rather than in single notes: with every group ask yourself which note carries the weight and which lead toward it. Take leading-toward notes lighter and let them press, instead of accenting them. With upbeat phrases it holds especially that the upbeat belongs to the following beat and not to the preceding bar — whoever takes it heavily cuts the line apart.