Thanks Victor.Hi YM-Mundrabilla,
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.