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?