We checked the handles anyone would try first. @faradaywaves has 86 followers and 11 posts, and its bio is a single line — faradaywavesband@gmail.com — so it is a band, not the fluid instability. @chladni has two followers and no posts at all. @cymatics is an account called "Sound" with 119 followers and two posts. @tonoscope has 39 followers and one post. @visiblesound has 24 followers, 15 posts and no bio.
That is the whole obvious namespace, squatted or abandoned. It matters because it explains why cymatics is so hard to find on Instagram: the keyword handles are held by people who are not posting, and the real accounts sit under names you would never search for, such as @seeing_into_the_unknown or @soundmadevisible.
Search by hashtag or by artist name instead of by handle.