Re: Re: Re: Re: Re: Re: Re: Re: Re: Flogging a dead horse...


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Posted by Rick Denney on February 05, 2003 at 12:21:12:

In Reply to: Re: Re: Re: Re: Re: Re: Re: Re: Flogging a dead horse... posted by JoeS on February 04, 2003 at 22:13:13:

I'd bet there are other differences between Bb and C trumpets that account for the effect you note, though I have no skill in determinine what they might be.

The notion of identical instruments in the two keys is actually impossible. A 186 C has the same bell stack, bottom bow, valve body, and tuning slide as a 186 BBb. If the bugle is five feet to the beginning of the tapered section (per my measurements) and five feet from the bell opening to the upstream end of the bottom bow (an approximate guess), then the tapered section in between is six feet long on the C and eight feet long on the BBb. The beginning and ending diameters are the same, so clearly the C has a faster taper. Therefore, comparing them is quite difficult. As Fred Young would say, the dimensionless ratios, which should be held constant when scaling instruments, vary.

We can't be guilty of inconsistency here. In ad after ad, it is considered ideal to maximize the ratio of conical to cylindrical tubing by using as few valves as possible. Graduated bores, short piston valve sections, short leadpipes, and so on are all justified by this purpose. Yet a BBb tuba does this by allowing less valve tubing to be used on most notes.

The Eb comparison to BBb doesn't hold. The C tuba uses a lower partial with less valve tubing on the notes between the BBb open tones and the CC open tones. These constitute only a few notes as I mentioned earlier. But the Eb tuba uses a lower partial with less valve tubing on the notes between the Bb and Eb harmonic series, which is a great majority of the notes in the scale of the instrument. With an F, nearly all the notes are played on a lower partial when compared with the Bb.

I suspect that if you compared two instruments that were perfectly scaled, so that the ratio of cylindrical tubing to conical tubing was the same, the taper was the same, the ratio of bore to bell diameter was the same, and the ratio of bore to length was the same, you'd get a clearer picture of the difference in sound between them. And I think there would be a difference. But contrabass tubas all seem to have the same bells, bottom bows, and valve bodies whether or not they are BBb or CC tubas. Thus, nominally identical CC tubas must have a faster taper. If that is the case, it begs the question concerning your trumpet example: Are nominally identical Bb and C trumpets of the same taper? I suspect that the C trumpet taper is about the same as the Bb trumpet taper (given that neither have much taper in comparison to a tuba).

Rick "still thinking of two bell curves that nearly completely overlap" Denney


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