My mountain bike has been creaking, and at least some of the noise was coming from my plastic minipump clip, which bolts onto the downtube, under the water bottle holder. When I torqued the frame, the holder rubbed against the downtube, which amplified the sound. Another source was the seat post / seat tube junction, with the top tube amplifying the sound.
__________________
"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069