Posted by Bob on June 23, 1999 at 15:39:00:
In Reply to: Partials ? posted by Paul H on June 23, 1999 at 15:07:13:
Basically, the partials are the notes you can play in open position (no valves). They are mathematically related in that their wave lengths and frequencies are in ratios of integers. The fundamental on a BBb tuba is the (very) low Bb. The second partial is the (normal) low Bb which has a frequency of twice the fundamental. The third partial is the F which has a frequency of 3 times the fundamental. The fourth partial is the mid-range Bb which has a frequency of 4 times the fundamental. This goes on with the partials getting closer together as they get higher.
The pitch of the fundamental is determined by the length of the tube. Use of the valves adds length to the tube which lowers the pitch of the fundamental and thereby also lowers all of the partials.
There are two basic problems. The first is that the frequencies of the notes determined by the diatonic (even-tempered) scale which we use does not match the pitches produced by some of the partials. The second is that adding the lengths of multiple valves does not produce the correct change in pitch. All of this leads to compensation which is a hot topic. On larger horns (tuba and euphonium) the errors are more pronounced and there is a lot more attention paid to their correction.
Hope this helps.