I agree tool use affects civilization, but the whole post is one radically different approach to metal using sophonts. :) I do not think the Singers' civilization(s) would be very human-like, driven by the wild biological differences more than the tool using similarities.
Agreed, written word would be difficult, but given clay and stone exist under water, I don't doubt there'd be equivalents of cunieform or Hittite available. Wood, cloth, paper and ink are likely not feasible underwater, but there are other options. Printing presses are likely a VERY advanced technology for those reasons, again causing cultural differences.
Thanks for commenting!