How tell if spokes too tight without tensionometer
Roger Musson's book "Professional Guide to Wheel Building" simply states that: "The best place to start when judging the correct tension is to examine a similar wheel you know to be good and reliable and compare the spoke tension to the one being built."

Musson does not use the sound of the spokes to determine their tension, only to find differences in tension between them.

Roger Musson's website does also have a good discussion about tensionmeters and their necessity when building wheels. http://www.wheelpro.co.uk/support/tensiometers/