# Resonant frequencies in organ pipes

I have a series of doubts regarding the principle of organ pipes. For a given length of closed organ pipe there are various modes of vibration for the standing waves.I dont know if this is silly but what decides the frequency of standing wave in the column,is it the frequency with which a person blows into pipe or are the frequencies or various harmonics dependent only on the length of column (the ones we calculate by drawing the number of waves in the column). What happens if the frequency of source cannot be matched by any of the possible variations of waves (harmonics), do we get low intensity of sound in such setups due to negative superpositions, how do we draw the standing wave inside the column then, will the closed end still be a node?
I was studying the resonance tube experiment to determine the speed of sound in air that lead me here. I understood till the part where loudness was maximum because the air in that particular length vibrated at the same frequency, the problem comes when we find the frequency at the second resonance length, why is that wave not in its first harmonic as depicted in any available picture of the experiment, does this imply that frequency of wave in column is determined by source?

• Blowing does NOT have a single frequency. – ggcg Dec 28 '19 at 15:22