Some instruments use wax or pellets to tune the fundamental pitch of each tube.
Only tiny adjustments will be needed then to adjust fundamental pitch for air density and temperature.
The fundamental pitch of the F horn is near that of the tuba.
Before valves became common in the 19th century, the horn could play only the notes of the overtone series from a single fundamental pitch.
Variations in the frequency of harmonics can also affect the perceived fundamental pitch.
Normally, we perceive only the fundamental pitch as being played.
Harmonics starting three octaves above the fundamental pitch are about a whole step apart, making a useful variety of notes possible.
The valves add tubing to the main tube of the instrument, thus lowering its fundamental pitch.
A string's fundamental pitch can be adjusted by changing its stiffness, which depends on tension and length.
This happens when sound waves strike the string at a frequency close to the string's fundamental pitch or one of its overtones.