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The natural range of a standard Bb trumpet, for example, extends down to F# (i.e., concert E), but by adjusting one's embouchure and air, it's possible to produce lower pitches. Those lower pitches -- pedal tones -- have a distinctly different timbre than the natural tones of the instrument -- duller and less brassy, less stable. Through practice they can be made useable and their timbre brought closer to that of other notes, but....

What is happening acoustically that makes pedal tones different? (Or, maybe, why can't brass instruments naturally produce those pitches in the first place?)


Related information

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  • Is this question limited to the trumpet, or does it apply to any valved brass instrument? – Richard Dec 23 '20 at 20:17
  • @Richard I limited it to trumpet only because I have no idea if the answer applies across brass instruments. If it does, the question should definitely be expanded. Let me know, and I'll rewrite – Aaron Dec 23 '20 at 21:27
  • This point concerns all brass instruments. – Albrecht Hügli Dec 23 '20 at 22:16
  • Would you like an answer that starts from scratch with the vibrating modes of cylinders closed at one end or just jump right ahead to how the pedal tones fit into the resonances of a bell and mouthpiece instrument? – Todd Wilcox Dec 25 '20 at 2:22
  • @ToddWilcox Quick answer: I think there's already a post covering the closed cylinder angle, so starting with the pedal tones seems best. Meanwhile, I'll see if I can track down the post I have in mind. If it's not there, expanding the question and answer seems appropriate. – Aaron Dec 25 '20 at 2:25
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Check here for the basics:

Trumpet Peculiar Frequency spectrum

In the above answer, it’s stated that the trumpet’s “natural” overtone series of only odd harmonics is altered by the flare of the bell and the shape of the mouthpiece so that instead of being only the odd harmonics, it has essentially a normal harmonic series, but the fundamental is missing.

A pedal tone is a way to play the “missing” fundamental. Any resonant system has a lowest resonant frequency and for bell and mouthpiece brass it’s there, it’s just not as easy to sound as the first harmonic and much of the series above it.

It’s also a different embouchure from the rest so pedal tones aren’t as frequently taught because many believe learning to play then might create bad embouchure habits in the student.

One thing about the above linked answer I’d be careful of is the reference to the clarinet, which does only have its odd overtones but is also a conical bore instrument so I think there are some subtleties beyond the half closed cylinder model at work in the clarinet.

There’s a Wikipedia article on the topic also.

Everything I’ve found suggests the concept of pedal tones applies to all members of the brass family, namely cylindrical bore metal instruments with a flaring bell and hemispherical mouthpiece that are primarily played by sounding an overtone series along with valves that change the sounding length of the primary cylinder. The fact that the horn uses a different mouthpiece shape doesn’t exclude it from the category.

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  • To confirm before I edit the OP, this applies across the brass family? Also, IMO, the last paragraph doesn't fit here, but would be valuable as a comment on the post it refers to. – Aaron Dec 25 '20 at 14:00
  • @Aaron I know the trombone is the same in acoustics. I believe tuba and euphonium is the same. Of course sax is not really a brass instrument (which you probably know but for other readers). I’m not sure about French horn, because I know horn mouthpieces are often conical and less hemispherical. I suspect it’s the same or similar but I’m not sure. – Todd Wilcox Dec 25 '20 at 17:54
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On any wind instrument, the basic idea behind the physics is that there's something vibrating at the front of the tube (the player's lips for brass instruments, the reed for reeded instruments, and air turbulence for flutes), which powers a vibration of air inside the tube, and the physics of constructive and destructive interference only allow a resonant frequency to ring out. The tone quality produced is determined by the spectrum of frequencies produced by the mouthpiece (and the skill of the player), refined by the characteristics of the resonator tube.

With trumpet pedal tones, you buzz a low frequency below the fundamental frequency of the tube, and "insist" on it hard enough that you overcome the physics of the resonator and force that pitch through. When this happens, the tube is no longer refining the tone as normal, and so the sound is just the mouthpiece buzz being saxamaphoned through the horn.

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  • Truthfully, you could have just written "saxamophone" and I still would have upvoted. – Aaron Dec 25 '20 at 3:39
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    My understanding is the pedal tones are not below the fundamental frequency but ARE the fundamental frequencies. Not pedal tones are not fundamentals, they are overtones. – Todd Wilcox Dec 25 '20 at 4:50
  • Yes, the pedal tone IS the fundamental. – Laurence Payne Dec 25 '20 at 16:07
  • @ToddWilcox No. Consider a note like F3. There is no length of tubing that makes this a fundamental. – MattPutnam Dec 25 '20 at 19:20
  • MattPutnam I don’t understand your comment above. My calculations are that a simple cylinder closed at one end and open at the other has a fundamental frequency very close to F3 if it is only 19.5” long. – Todd Wilcox Dec 25 '20 at 20:41
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Much the same as the acoustics of any other note. Just somewhat harder to produce due to the proportions of the instrument and mouthpiece.

More interesting are the 'false' notes between pedal (written) C and F♯, bottom of the 'normal' range. There is a definite F fingered 1-2, E fingered 2-3 etc. (i.e. one fingering 'lower' than might be expected). You have to force them, but they definitely exist and with practice can almost match the normal notes.

On trombone, the pedal notes are easier (wider tube, larger mouthpiece) and are routinely asked for. The 'false' notes are also easier, but unlike the pedals are not normally asked for except as an 'extended technique'.

Modern trombones (especially bass trombones) have switchable extension tubing that enable the lower range without trickery. But the characteristic rasp of a smaller instrument's pedal tones is still useful.

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  • This is very cool and deserves more visibility than it will get here. Opening a separate question.... – Aaron Dec 25 '20 at 17:13
  • New question opened. – Aaron Dec 25 '20 at 17:21
  • "There is a definite F fingered 1-2, E fingered 2-3 etc." -- uh, no there isn't. Where is this coming from? – MattPutnam Dec 26 '20 at 2:49
  • According to this post the trumpet isn't capable of "false tones". Reading your post again, I think I understand the conflict. The notes below the "lowest" F# are "pedal tones" -- the subject of the question -- "false tones", which are related the bore-width vs. length ratio, aren't achievable on the trumpet, because its bore is too narrow. – Aaron Dec 28 '20 at 2:52
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    @Edward Okay, I think I found the problem. "Pedal tones" on a trumpet are something of a misnomer. 'trumpet players usually talk about the pitches between low F# and pedal C also as “pedal tones.” In contrast, other brass players tend to call those “fake tones.”' (Source). – Aaron Dec 28 '20 at 3:21

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