Those Paetzold square recorders are actually quite excellent. I saw the superb Amsterdam Loeki Stardust Quartet using one or two of them a couple of years ago and they sounded terrific-- sort of like organ pipes. The keys (also plywood) make a cool clacky sound and one of the modern pieces the quartet played actually used that clacky sound without blowing the recorders!
Edgar Varese’s Density 21.5?
He got the density wrong, apparently. (It was written for an owner of a platinum flute) It was said to be the first piece written to incorporate flute key noise.