A scale is committed to how long its instrument rings
Assumes: The smoothness is in the skips · The scale least committed to its own instrument
The smoothness is in the skips counted a scale’s roughness over the pairs of notes its plainest melody sounds, and counted them by distance: each note with the next, or with every note up to some number later. Counted by the steps, every seven-note scale was rougher than nine random scales in ten; counted by the skips, and above all by the fifths four notes apart, the same scales were among the smoothest there are. And the prediction the scale least committed to its own instrument had recorded — that weighting the pairs would make each scale’s standing depend more on the instrument — held only once enough of the melody was counted.
Its last section said what the distance was standing in for. Roughness is a property of two sounds at once, and a melody’s notes come one at a time, so a step is rough only as far as the note before is still sounding when the next begins. A distance counts every pair within it fully and every pair beyond it not at all. A real instrument does neither: it rings, and the note before fades by an amount set by the instrument and by the tempo. Replacing the distance with the ring puts the instrument into the measurement a second time — once in the partials, and once in how long they last.
The result of doing that is that the second appearance is nearly the whole of it.
A ring instead of a distance
The ring is one law with two numbers in it. The note before loses sixty decibels at its fundamental in a decay time, and loses its upper components faster, in proportion to their frequency ratio raised to a power. A power of one means a component at three times the fundamental dies three times as fast; a power of nought means everything dies together. The laws used here are the ones the partials that do not die together set down for a plucked string, a long-sustaining string and a free bar, which that essay was careful to call ordinal rather than measured, and the blown note is a note that stops when the next one starts and is heard in a hall whose reverberation time is two seconds — a room of the kind a concert hall is built to be.
A pair of notes is then scored by the same Plomp–Levelt model every roughness figure in these essays has used, but between two different spectra: the later note’s, as struck, and the earlier note’s, as it stands at that moment. Every pair the melody sounds is counted, at every distance, until the earlier note’s fundamental is sixty decibels down. A score per note of melody is compared with the same score for two thousand random scales walked by the same melody, as before, so a percentile still says where a tradition’s scale sits among the scales it could have been.
Two properties of the construction matter for everything that follows. With every component decaying at the fundamental’s rate, the ring at one distance is a single number for every pair, so a ring that stops after one note is exactly the count of steps, and each column of pairs at one distance is exactly the earlier count at that distance — both are checked percentile for percentile. And the score reads a ring only through the time between notes divided by the decay time, so halving every decay time is exactly the same as doubling the time between notes. A decay time that is wrong by a factor is a tempo that is wrong by the same factor, and that is the most a borrowed decay time can distort here.
With nothing decaying faster, the skips still carry it
With every component decaying together, the ring reproduces the earlier finding under the plucked string’s spectrum as well as the tanpura’s. The steps are the roughest pairs a seven-note scale has and the fifths the smoothest: 97.0 to 98.6 one note apart, and 0.0 or 0.1 four notes apart. The pentatonic scales keep their own pattern, with Bhupali’s steps at 56.8 and its thirds and fourths two notes apart at 3.0, and the slendro’s at 44.5 and 3.6.
That is the control. It says that the change of instrument, as far as the spectrum goes, does not alter where a scale’s smoothness is located.
The partials that make a fifth smooth are the first to go
A fifth is smooth in this model for one reason, which a spectrum chooses its own scale put at the centre of the account: the third partial of the lower note lands on the second partial of the upper, and a coincidence contributes no roughness. A plucked string’s third partial is the component that, on its law, dies three times as fast as its fundamental. By the time a note four notes later begins, at a note every 0.3 seconds, it is 36 decibels down.
Let the upper components decay at their own rate and the fifths lose their place. Four notes apart, the seven-note scales go from 0.0 or 0.1 to between 13.1 and 18.8 — still smoother than most random scales, no longer smoother than all of them. The smoothest distance becomes two notes apart, where the pairs are mostly thirds and the note before has had half as long to lose its upper partials, at 6.2 to 9.2. The steps are rougher still, at 98.9 to 99.8, because the earlier note of a step is now closer to a pure tone, and a pure tone keeps the rough steps: they belong to the critical band and not to the partials.
So the division of labour the earlier essay found is sharpened rather than overturned. The critical band makes a scale’s steps rough whatever is sounding, and the partials make its fifths smooth — but only while the partials last, and on a plucked string they last a third as long as the note does.
Rings, not spectra
Back at a note every 0.6 seconds and with each instrument’s own spectrum and ring, the four seven-note scales move 30.9 to 37.0 percentile points across the four instruments, which is more than any distance weighting moved them: counting only steps they moved 6.0 to 6.6, and counting everything within eight notes 16.6 to 22.1. The instrument matters more once it is allowed to ring. What the first figure cannot say is which half of the instrument is doing it.
The four columns separate the two halves. Put all four rings on one spectrum — the tanpura’s sixteen harmonics — and every scale moves almost exactly as far as it does with the real instruments: the tempered diatonic 38.6 against 37.0, the Turkish Rast 35.4 against 35.5, the slendro 15.0 against 18.6. Put all four spectra under one ring, the plucked string’s with its components decaying together, and the tempered diatonic moves 9.4; with its upper components decaying faster, 2.8. For every one of the seven scales, the rings alone move it at least three quarters as far as the instruments do, and the spectra alone half as far or less.
The reason the tilted column is the smallest of all for the seven-note scales is the section above. A ring that strips the upper partials from the note before strips out exactly the thing that distinguished the spectra, and four spectra with their upper partials gone are four spectra much more alike. The long ring is what separates the instruments: the long-ringing string is the smoothest of the four for every scale, because it keeps the note before sounding long enough for the skips to be counted, and the skips are where a scale’s smoothness is.
The order of the four instruments is as regular as that. At a note every 0.6 seconds the long-ringing string, losing three decibels a note, is the smoothest instrument for every one of the seven scales, and the free bar is the roughest for every one of them: its partials do not coincide at the fifth, and its ring of four seconds is long enough to count its rough skips as well as its steps. The two in between trade places by scale size. The blown note, which the hall takes down eighteen decibels a note at this tempo, is the second smoothest instrument for all three pentatonic scales and the second roughest for all four seven-note ones. A ring that short counts little beyond the steps, and the steps of a pentatonic scale are wide enough not to be rough while the steps of a seven-note scale are the roughest pairs it has. The instrument is not ranked by its spectrum or its ring alone but by what its ring lets a scale’s own steps and skips do.
That answers the question the debt put. A scale’s commitment to its instrument is a commitment to how long the instrument sounds, at least at this tempo and on these four laws. The account that a spectrum chooses a scale explains where a scale’s smoothness is; it does not explain why the same scale stands in a different place on a different instrument.
Two ragas on one set, and two Rasts
A degree is where it goes next made Bhupali and Deshkar the test case for any measure of a scale’s sound, because they have the same five pitches and different ascents. Counted by distance, they came apart in two directions: one note apart Deshkar was the smoother, because its ascent leaps a third where Bhupali takes two whole tones, and two and four notes apart Bhupali was, because the leap puts Deshkar’s later pairs out of step.
The ring decides between those two answers, and it decides the same way on every instrument. At a note every 0.6 seconds Deshkar is the smoother raga under all four, by between 9.9 and 16.5 percentile points: 39.0 against 53.6 on the plucked string, 25.9 against 35.8 on the long-ringing one, 26.1 against 41.3 for the blown note, and 42.0 against 58.5 on the bar. The distance tables under the plucked string’s own ring at 0.3 seconds keep the split the earlier essay found — Deshkar smoother one note apart, 46.3 against 68.3, and Bhupali smoother two and four notes apart — but a ring does not weight the distances alike. It counts the nearest pairs most, because the note before has faded least by the time they sound, and the nearest pairs are where Deshkar’s leap buys it smoothness. Weighted by what is actually still sounding, the leap in Deshkar’s ascent is worth more than it costs.
The two conventions for Rast differ in one respect, the size of their neutral steps, and they come out in one order too. The Arabic convention, four of whose seven steps are 150 cents and sit on the peak of a pure tone’s roughness, is rougher than the Turkish on every instrument: by 4.0 points on the plucked string, 7.1 on the long-ringing string, 1.5 for the blown note and 2.5 on the bar. The margin is widest on the instrument with the longest ring, which counts the most pairs and so gives a difference in step size the most pairs to show up in.
At every tempo but the fastest
The split depends on the tempo, and it holds everywhere except at the fastest. At a note every 0.15 seconds — a quick ornamental run — the tempered diatonic moves 15.5 points across the instruments and 14.8 across the spectra under one ring, so there the spectra account for nearly all of it: every ring is long compared with the notes, all four instruments count the skips, and what is left to differ is the partials. From a note every 0.3 seconds to one every 0.6 the instruments move it 35.4 to 38.7 points and the spectra 8.6 to 9.5. By 1.2 seconds a note both are smaller again, 16.8 against 11.2: on every instrument the note before has faded further by the time each later note begins, the steps count for more on all four, and the four differ less.
The pentatonic scales are less dramatic and go the same way. The slendro moves 9.2 at 0.3 seconds and 32.2 at 1.2, against 4.8 and 9.4 across the spectra; Bhupali 14.1 against 12.4 at 0.3, where its two numbers come closest, and 30.7 against 9.3 at 1.2. The ordering of the scales changes with tempo too. At a note every 0.6 seconds the scale that moves least is Deshkar, at 16.1, and not the slendro, which moves 18.6; at 1.2 seconds the slendro moves more than Bhupali or the diatonic. The earlier finding that the slendro is the least committed scale was a finding about a measurement with no tempo in it.
The arithmetic
Each melody is the cycle its ascent and descent describe, as in the essay before this one, and the notes are evenly spaced at the stated time between notes. For a pair in which the earlier note sounded t notes before the later, each of the earlier note’s components is multiplied by ten to the power of minus three times t times the time between notes times its ratio to the law’s exponent, divided by the decay time, which is sixty decibels in the decay time at the fundamental. The pair’s roughness is the Plomp–Levelt sum over every component of the earlier note against every component of the later, the tonic at middle C, and the scale’s score is the sum over every pair the cycle sounds, per note of the cycle, until the earlier note’s fundamental has fallen sixty decibels.
Because that score is linear in the earlier note’s component amplitudes, it is computed as a table of component roughnesses for each scale multiplied by a table of ring weights for each melody, instrument and tempo, and the two thousand random scales are the same scales, drawn from the same seed, that every percentile in these essays has used. The laws are the plucked string of six seconds with an exponent of one, the long-sustaining string of twelve with 0.7, a free bar of four with 0.5, and the blown note in a hall of two seconds with none.
What the ring assumes
That the laws are right in order if not in size. They are ordinal laws carried over from the essay on partial decay, and a uniform error in their decay times is a change of tempo, which the tempo figure covers. An error that changed their order — a bar that rang longer than a plucked string at middle C, say — would change which instrument is smoothest and not whether the rings dominate.
That the long-ringing string stands for a tanpura-like instrument. The tanpura’s spectrum is sixteen harmonics; its ring here is the long-sustaining string’s law, borrowed rather than measured. The column that puts every ring on the tanpura’s spectrum is not affected, and it is the one the conclusion rests on.
That the pair is scored at the moment the later note begins. The earlier note goes on fading while the later one sounds, and the later one fades too. Scoring the overlap over the whole of the later note would shrink every weight, the far ones more, which is a small shift towards the steps.
And that notes are evenly spaced and nothing is damped. A saron player damps each bar with the free hand as the next is struck, which cuts the ring of the note before exactly when the pair would begin: under this measure a damped bar sounds no pair of notes at all, and whatever roughness its melody has in succession is the hall’s. A room does not decay evenly either, and a hall’s own colour on the note before is not modelled.
What a ring cannot show
That listeners hear a scale’s roughness in succession. The measure scores what sounds together, and a melody heard one note at a time is also heard in memory, where nothing decays at sixty decibels in a fixed time. The ring is the physical half of the question.
That traditions chose instruments to suit their scales, or scales to suit their instruments. The arithmetic says that a sustaining instrument makes the skips count and a quickly fading one makes the steps count, and that the commitment to an instrument lives there. Roughness cannot choose a scale is still the limit on what that can explain, and consonance is half learned is still the other half.
Still open: the gamelan’s bar, damped and undamped
The free bar here is an ideal one, and the spectrum that was supposed to explain the gamelan found that a bar’s partials do not recommend a slendro. A gamelan is played two ways on the same bars: the saron’s bars damped at every stroke, and the gendèr’s left to ring over their resonators and damped more selectively. With the ring in the measurement those are two different instruments with one spectrum, and the next computation is the slendro’s commitment between them — a ring cut at the next stroke, a ring left to run, and the resonator tubes that lengthen it — at the tempo levels a gamelan piece moves through. It would say whether a slendro’s standing depends on how it is struck more than on what it is struck on, and whether the damping practice is the one that makes the scale’s steps rough or the one that keeps them from sounding at all.
Part 11 of 14
One essay in the series on beyond twelve. The essays either side of this one:
What this makes readable
Essays that declare this one a prerequisite.
The objects named here
The third way in, after the field and the series: the things themselves, and every essay that touches each one.
Critical bandwidthDecayMelodic intervalNull modelPentatonicPlomp–Levelt curveRagaReverberationSensory dissonance
- Roughness can be computed, and the answer looks like a scale critical bandwidth, plomp–levelt curve, sensory dissonance
- A damper cannot reach into the room decay, reverberation
- A dissonance has to last critical bandwidth, sensory dissonance
- A fifth on a piano is not a fifth a second later critical bandwidth, decay
- A low chord stops being rough by stopping being a chord critical bandwidth, sensory dissonance
- A room keeps a pizzicato from giving its note away decay, reverberation