Talk:Pseudo-octave

Additional citations
Good article; it's unclear how widespeard the term is, as opposed to the practice. Sparafucil 04:42, 24 June 2007 (UTC)

What else needs to be verified or cited? Hyacinth (talk) 01:52, 17 August 2008 (UTC)


 * Tag removed. Hyacinth (talk) 22:23, 27 April 2011 (UTC)

It's all too easy to put a 'citation needed' tag on things that don't really need them. If a paragraph already has inline citations in several places, then it is unfair to add additional 'citation needed' tags unless an important fact is being called into question. That some (unspecified) person uses a particular (but obvious) variation of a term in a particular way does not rise to the level of controversy required for a 'citation needed' tag, IMO. Two tags are being removed. Dlw20070716 (talk) 17:23, 7 August 2011 (UTC)

"Cause" of stretched octaves
Stretched octaves are caused by the physics of standing waves in a stretched wire.

No they're not. They're "caused" by the way the piano is tuned. The reason that this tuning is desirable has to do with the physics of standing waves. —Preceding unsigned comment added by 68.239.116.212 (talk) 06:33, 29 January 2010 (UTC)

"Stretched octaves are caused by the physics of standing waves in a stretched wire. The pitch of each overtone produced by a piano string is determined by the ratio of the string's restoring force (expressed as a spring constant), divided by its mass per unit length. In an ideal piano string, the only restoring force would be due to the tension in the string. In practice, piano strings are made from high-carbon steel, which is stiff. Young's modulus of the string steel (tempered high-carbon steel) is what defines the stiffness and does not change with the temper. The stiffness adds an extra restoring force to each string; the amount of this extra force depends on the amount of bend being induced in the string. Higher normal modes bend the string more, inducing more stiffness-related force and sharpening the pitch of the resulting overtone."

I'm sorry, but this sounds like BS to me. I don't believe there is any significant "restoring force" in a piano string caused by its stiffness. I agree with the pitch being determined by the mass per unit length and the string tension, but the restoring force has nothing to do with the tension of the string. This would violate all sorts of Newton's laws. The fundamental vibrational mode of a stretched string is such that the wavelength is twice the length of the string. The standing waves mentioned here are set up by the harmonics of the fundamental which are distributed in number and intensity according to the mass of the string. The bass strings on a guitar, for example, are wound with wire radially, to give them more mass without increasing the stiffness, thus allowing it to produce the desired mix of harmonics. Piano strings are made from high-carbon steel to make them stretch-proof, not to make them into springs. The real explanation for use of the so-called Pseudo-octave would be that some vagaries of the instrument as a whole cause it to sound "wrong" when properly tuned; so the "band aid" remedy is to detune it. This has to be all wrong. The instrument should be redesigned.

Have a look here:

Freddy011 (talk) 06:03, 1 December 2016 (UTC)

Actually, this is bothering me so much, because it is so wrong, that I am going to rewrite the whole thing, after a reasonable length of time without anyone objecting to the idea. I just abhor the spreading of misinformation.

Freddy011 (talk) 13:24, 1 December 2016 (UTC)

"Citation Needed" just doesn't do it. The whole thing is WRONG.

Freddy011 (talk) 13:32, 1 December 2016 (UTC)

OGG sample would be better
It would be better if our examples were not MIDI. Ideally, we'd have four samples: a theoretically perfect octave on an ideal instrument, a perfect octave on a real instrument, a stretched octave on a real instrument (so that it sounds in tune), and that same stretch on an ideal instrument (which will not). — trlkly 06:48, 26 September 2010 (UTC)


 * Feel free to create these samples. Hyacinth (talk) 07:00, 27 September 2010 (UTC)

Piano strings do not store "acoustic" energy
"long strings under high tension can store more acoustic energy than can short strings, giving larger instruments more volume" It is correct that they can store more energy, but that energy does not report as acoustic energy until it is transformed into such by causing motion in the medium (air) in which the strings themselves move, at which time it is no longer stored in the string but in the air. While it is in the string it takes the form of (strain energy due to tension at time t) + (kinetic energy due to string mass and velocity at time t). This sum reflects the time-varying partition of the stored energy circulating in a "tank circuit": when the string passes through its equilibrium position the strain energy is minimal because the tension is and the kinetic energy is maximal because the velocity is, and when the string is at its maximum displacement the strain energy is maximal because the tension is and the kinetic energy vanishes because the string is motionless. This is exactly analogous to a pendulum clock: the pendulum stores PE(t) + KE(t) units of energy at time t where PE is the potential energy and KE is the kinetic energy, with the analog of the acoustic energy being the amount of energy being withdrawn from the tank circuit (PE and KE being the two "tanks" between which the stored energy flows back and forth) and dissipated by the clockworks. Lewis Goudy (talk) 05:33, 18 June 2021 (UTC)

This is non-sensical: "In piano tuning, stretched octaves are commonly encountered in instruments where string thickness and high string tension causes some strings to approach their elastic limit, which makes the string respond to stretching and bending with a pull to restore its original shape and position a little out of proportion to how far it was bent or stretched. That non-linearity causes small differences between the string's real overtone frequencies and the mathematically ideal simple harmonic oscillator's integer multiple harmonics."

This, too, is errant: "Octave stretching is less apparent on large pianos which have longer strings and hence less curvature for a given displacement; that is one reason why orchestras go to the expense of using very long concert grand pianos rather than shorter, less expensive baby grand, upright, or spinet pianos." Octave stretching is what the tuner does to accommodate a piano's inherent inharmonicity. Joelthesecond (talk) 14:55, 30 March 2024 (UTC)