Delay between play and sound
Depending on the instrument, the length of organ pipes can exceed 10 meters. At such lengths, it can seem that there is a delay between pressing a key on the manual and the sound being produced, but actually this is not the case. Like pushing jelly from a bamboo cane, the wind in the pipe forms an air column (akin to the pillar of air that fills the space within a tube), and because this is pushed from below sound is produced according to the amount of wind that enters the pipe. This doesn't occur faster than the speed of the wind, but there isn't a delay substantial enough to be noticeable while listening.
That said, if someone were to listen exceptionally closely, there might be a very slight difference between the high notes and the low notes. The pipes for the high notes are short and thin, and the sound is produced in an instant, whereas those for the low notes are wide and long, so the oscillation of the air column takes a little longer to establish, and the note finishes playing a little later. For this reason, when five pipes of different lengths are played together, the tones sound from the highest in order, and the last sound to fade is the lowest tone.