In the case of an organ pipe, it is usually designed to furnish you with the fundamental (lowest) note it is resonant at. Here's how.
An organ pipe which is excited by compressed air has a rather complicated assembly of bent and curved metal pieces situated at its blown end. The objective of that arrangement is to preferentially set the pipe into oscillation at its fundamental. This occurs when the compressed air being carefully blown past its end is set into back-and-forth motion right next to and then away from the pipe opening: when a positive pressure pulse exits the blown end of the pipe, it deflects the air stream away from the pipe end; when a negative pressure pulse follows it, it sucks the air stream back in towards the pipe opening.
That arrangement of metal sheets also provides a short burst of hissing noise from which the organ pipe filters out its fundamental and radiates it. clever design of the hiss maker can make it produce a whooshing noise (good for exciting the bass note pipes) or a sharper hissing noise (good for exciting the higher note pipes).
This whole business was worked out by trial and error by medieval craftsmen hundreds of years ago; what I have furnished here is just an extremely simplified picture of an extremely complicated business!