i did this simple test about six years ago: bought a 1/2 dozen stemmed wine glasses and dipped 2 of each in a different container of lacquer, poly-urethane, and the kind of shellac that came in "flakes". i tried to mix the shellac flakes and the poly-urethane to the same viscosity as the lacquer, then a "watch the liquid drip off the chopstick test" then i hung them up to dry for a few weeks. 1st test was a simple "ping" with a flick of a finger nail, next was bowing with a fiddle bow, lastly was filling them 1/2 full of water and circling the rim with a wet finger. the glasses giving the brightest tone were those dipped in flake shellac, darkest were those dipped in poly. i'm told that flake shellac continues to harded over the years so i suspect any tonal quality that it imparts will be effected...er affected to make it even brighter. this is what happens when people have too much time on their hands......... my hardware store didn't have a can of polyester coating but i imagine it to be similar to poly-urethane.....i don't know why, i just suspect that they're similar. fwiw i did a saddle test with the wound "A" and "D" strings on three separate fender thinlines of the mim variety. the small steel saddles with the grooves were the brightest and about the same as the fat aluminum glendale saddles, and as one would expect, the brass saddles made the wound strings less bright than did the other saddles............. i didn't have fat steel or skinny aluminum saddles to test with.. once again, a bit too much time on the hands. those are my unscientific test results. the thinlines were all mahogany... we all have different feelings for what we perceive as "good" tone..... i like the wound "E" to sound like the same pitch on a piano, bright clear and sparkley.