The notes of a whistle on air and on steam will be different.
The fundamental wavelength of the sound will be a mix of integer fractions of the the whistle's length. Frequency x wavelength = sonic velocity. The sonic velocity of air and steam are different. The speed of sound of 20 deg C air is about 345 m/s and is roughly proportional to the the square root of the absolute temperature. (it is proportional for an ideal gas and equals the square root of Gamma x R x T/M) The speed of sound in steam varies with both the temperature and the pressure. The fundamental frequency will be different and the mix of harmonics will be different.
Last edited by Victor J. Croasdale; 18th May 2018 at 17:32..