Coltman, J.W. (1990). Mode stretching and harmonic generation in the flute. J. Acoust. Soc. Am. 88, 2070-2073

Comparison of the resonance frequencies of modes in conical and cylindrical piccolos showed pronounced differences in the degree to which the octaves are stretched. Measurements for a note on a flute with only two modes showed that second harmonic generation and total radiated power were greatest when the modes were stretched 25 cents from an exact octave, supporting the idea that mode stretching may be beneficial in flutelike instruments.