I really like this concept. It's very unique compared to other things I've encountered, and I like that you've thought out what technology level they'd have and found a creative reason for it. One thing I'd be interested in is whether the Singers have any beliefs about the natural rhythms of the ocean - do you think that tides, currents, et cetera produce vibrations that have philosophical or religious connotations for them? Are the piezoelectric crystals you mentioned considered sacred, or just tools?
Thanks! I hope people start working on their own unique takes - there's tons of room to grow beyond bumpy-headed humans. (I've nothing against BHH's, they can be quite fun, but I would love to have ever-broader options.)
I hadn't grown the concept in those areas. I had notions of clusters of families of choirs as the base nation concept. Given the eventual size of some of their tooling, as well as limited livable space (underwater to a certain depth, avoiding 'deserts' with low microbiota counts) would tend to clump populations, so a city-state-like scenario at various early times in their development is IMO probable. Beyond those physical constraints, I've little thought on what keeps these clumps working smoothly. As their microbiota husbandry skills increase (IF they increase - I'd tend to think they would as they want big families for defense-in-depth of their vulnerable Soft Seasons) they could expand the 'sweet spots' for life to cover much more terrain, but there'll still be limits based on depth. Dredging (both from deeper waters and to make shallow water zones out of coastal lands) are possible extents but both are intensive efforts, so much like humans there'll be the whole property value coming down to 'location, location, location'.
Hadn't considered religion/philosophy. What drives a syphonovore's belief set? How did early Singers deal with population pressures? I've no answer off the top of my head, but I certainly thank you for the questions - I do like brain-stretching like this!