Word that Describes the Motion of an Accordion
Undulation refers to a wave motion:
From the VERB Undulate:
[NO OBJECT]
- Move with a smooth wave-like motion:
It's original meaning was a wave in water:
Undulate: 1640s, from Medieval Latin *undulatio, from Late Latin undulatus "wavy, undulated," from undula "wavelet," diminutive of Latin unda "wave"
(see water (n.1)). > Old English wæter, from Proto-Germanic *watar (cognates: Old Saxon watar, Old Frisian wetir, Dutch water, Old High German wazzar, German Wasser, Old Norse vatn, Gothic wato "water"), from PIE *wod-or, from root *wed- (1) "water, wet" (cognates: Hittite watar, Sanskrit udrah, Greek hydor, Old Church Slavonic and Russian voda, Lithuanian vanduo, Old Prussian wundan, Gaelic uisge "water;" Latin unda "wave").
It would not be unreasonable to extend the application to the wave of air caused by the bellows of the accordion, or the motion of the accordion itself. But then, you could opt for the simpler
Wave:
From the VERB wave:
[NO OBJECT]
- Move to and fro with a swaying motion while remaining fixed to one point:
NOUN
- Physics A periodic disturbance of the particles of a substance which may be propagated without net movement of the particles, such as in the passage of undulating motion, heat, or sound.
Pulsation feels good with regard to an accordion:
From the VERB pulsate:
[NO OBJECT]
- Expand and contract with strong regular movements:
When you watch an accordion player, you see of the bellows expand into an arc, and then compress into a rectangle again. The expansion into an arc could be described as:
Billowing,
which also evokes the bellowing sound an accordion can make.
Of course, during its expansion the accordion is
Swelling
Sinusoidal, adjective
si·nu·soi·dal \ˌsīn-yə-ˈsȯi-dəl, ˌsī-nə-\
of, relating to, shaped like, or varying according to a sine curve or sine wave; sinusoidal motion; sinusoidal alternating current; sinusoidal grooves -merriam-webster.com
— adverb: sinusoidally
Looking at the video of this virtuoso at play, there are many techniques an accordionist uses for expression. (I particularly like the staccato pulsing at the very beginning of this video.)
For the life of me, I cannot determine one word which can encompass all the variations of accordion movement.