The conical horn converts a closed-reed tube into a full harmonic instrument

Evidence

The upshot is that a cutoff cone closed at its narrow end is a lot like a double-open cylinder of the same length. The resonances form a harmonic series, with every frequency represented (no missing partials, unlike the clarinet, which is a half-open cyclinder). The angle between the axis of the cone and its walls can be as little as 1/2 degree in some instruments. An oboe’s bottom note is an octave higher than a clarinet of the same length. — Eric J. Heller, Why You Hear What You Hear- An…, 1472 (#corroborates, via linked claim)

In a complete brass instrument, it is possible through the use of an appropriately shaped bell, mouthpiece and mouthpipe to construct an instrument whose modes are frequency shifted from the odd-only modes of a stopped cylindrical pipe to being very close to a complete harmonic series. In practice, the result is a harmonic series in which all modes are within a few percent of being integer multiples of a common lower-frequency value except for the first mode itself, which is well below that lower-frequency value common to the higher modes, and therefore it is not harmonically related to them. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1250 (#corroborates, via linked claim)

Categorization

• XREF: connects to: A closed narrow-end cone acts like a double-open cylinder giving all harmonics — Eric J. Heller, Why You Hear What You Hear- An…, 1472; Brass instrument design transforms odd-only pipe modes into a near-complete harmonic series — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1250; Even harmonics appear in clarinet sound despite its closed cylindrical resonator (+1 more)

Broader Connections

• A closed narrow-end cone acts like a double-open cylinder giving all harmonics #corroborates (0.95) — Eric J. Heller, Why You Hear What You Hear- An…, 1472
• Brass instrument design transforms odd-only pipe modes into a near-complete harmonic series #corroborates (0.90) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1250
• Open-open and open-closed tubes produce different harmonic series #expands (0.80)
• Even harmonics appear in clarinet sound despite its closed cylindrical resonator #complicates (0.75)