#jsDisabledContent { display:none; } My Account | Register | Help

# Bohlen–Pierce scale

Article Id: WHEBN0000321868
Reproduction Date:

 Title: Bohlen–Pierce scale Author: World Heritage Encyclopedia Language: English Subject: Collection: Publisher: World Heritage Encyclopedia Publication Date:

### Bohlen–Pierce scale

Chord from just Bohlen–Pierce scale: C-G-A, tuned to harmonics 3, 5, and 7. "BP" above the clefs indicates Bohlen–Pierce notation.

The Bohlen–Pierce scale (BP scale) is a musical tuning and scale, first described in the 1970s, that offers an alternative to the octave-repeating scales typical in Western and other musics,[1] specifically the equal tempered diatonic scale.

The interval 3:1 (often called by a new name, tritave) serves as the fundamental harmonic ratio, replacing the diatonic scale's 2:1 (the octave). For any pitch that is part of the BP scale, all pitches one or more tritaves higher or lower are part of the system as well, and are considered equivalent.

The BP scale divides the tritave into 13 steps, either equal tempered (the most popular form), or in a justly tuned version. Compared with octave-repeating scales, the BP scale's intervals are more consonant with certain types of acoustic spectra.

The scale was independently described by Heinz Bohlen,[2] Kees van Prooijen[3] and John R. Pierce. Pierce, who, with Max Mathews and others, published his discovery in 1984,[4] renamed the Pierce 3579b scale and its chromatic variant the Bohlen–Pierce scale after learning of Bohlen's earlier publication. Bohlen had proposed the same scale based on consideration of the influence of combination tones on the Gestalt impression of intervals and chords.[5]

The intervals between BP scale pitch classes are based on odd integer frequency ratios, in contrast with the intervals in diatonic scales, which employ both odd and even ratios found in the harmonic series. Specifically, the BP scale steps are based on ratios of integers whose factors are 3, 5, and 7. Thus the scale contains consonant harmonies based on the odd harmonic overtones 3/5/7/9 (   ). The chord formed by the ratio 3:5:7 (   ) serves much the same role as the 4:5:6 chord (a major triad    ) does in diatonic scales (3:5:7 = 1:1.66:2.33 and 4:5:6 = 2:2.5:3 = 1:1.25:1.5).

## Contents

• Chords and modulation 1
• Timbre and the tritave 2
• Just tuning 3
• Bohlen–Pierce temperament 4
• Intervals and scale diagrams 5
• Music and composition 6
• Symposium 7
• Other unusual tunings or scales 8
• Sources 9

## Chords and modulation

3:5:7's intonation sensitivity pattern is similar to 4:5:6's (the just major chord), more similar than that of the minor chord.[6] This similarity suggests that our ears will also perceive 3:5:7 as harmonic.

The 3:5:7 chord may thus be considered the major triad of the BP scale. It is approximated by an interval of 6 equal-tempered BP semitones (   ) on bottom and an interval of 4 equal-tempered semitones on top (semitones: 0,6,10;    ). A minor triad is thus 6 semitones on top and 4 semitones on bottom (0,4,10;    ). 5:7:9 is the first inversion of the major triad (0,4,7;    ).[7]

A study of chromatic triads formed from arbitrary combinations of the 13 tones of the chromatic scale among twelve musicians and twelve untrained listeners found 0,1,2 (semitones) to be the most dissonant chord (   ) but 0,11,13 (   ) was considered the most consonant by the trained subjects and 0,7,10 (   ) was judged most consonant by the untrained subjects.[8]

Every tone of the Pierce 3579b scale is in a major and minor triad except for tone II of the scale. There are thirteen possible keys. Modulation is possible through changing a single note, moving note II up one semitone causes the tonic to rise to what was note III (semitone: 3), which thus may be considered the dominant. VIII (semitone: 10) may be considered the subdominant.[7]

## Timbre and the tritave

3:1 serves as the fundamental harmonic ratio, replacing the diatonic scale's 2:1 (the octave). (   ) This interval is a perfect twelfth in diatonic nomenclature (perfect fifth when reduced by an octave), but as this terminology is based on step sizes and functions not used in the BP scale, it is often called by a new name, tritave (   ), in BP contexts, referring to its role as a pseudooctave, and using the prefix "tri-" (three) to distinguish it from the octave. In conventional scales, if a given pitch is part of the system, then all pitches one or more octaves higher or lower also are part of the system and, furthermore, are considered equivalent. In the BP scale, if a given pitch is present, then none of the pitches one or more octaves higher or lower are present, but all pitches one or more tritaves higher or lower are part of the system and are considered equivalent.

The BP scale's use of odd integer ratios is appropriate for timbres containing only odd harmonics. Because the clarinet's spectrum (in the chalumeau register) consists of primarily the odd harmonics, and the instrument overblows at the twelfth (or tritave) rather than the octave as most other woodwind instruments do, there is a natural affinity between it and the Bohlen–Pierce scale. In early 2006, clarinet maker Stephen Fox began offering Bohlen–Pierce soprano clarinets for sale. He produced the first BP tenor clarinet (six steps below the soprano) in 2010 and the first epsilon clarinet (four steps above the soprano) in 2011. A contra clarinet (one tritave lower than the soprano) is under development.

## Just tuning

A diatonic Bohlen–Pierce scale may be constructed with the following just ratios (chart shows the "Lambda" scale):

 Note Name Degree Ratio Cents Midi Step Name Ratio Cents C D E F G H J A B C 1/1 25/21 9/7 7/5 5/3 9/5 15/7 7/3 25/9 3/1 0 301.85 435.08 582.51 884.36 1017.60 1319.44 1466.87 1768.72 1901.96 T s S T s T S T s 25/21 27/25 49/45 25/21 27/25 25/21 49/45 25/21 27/25 301.85 133.24 147.43 301.85 133.24 301.84 147.43 301.85 133.24

A just BP scale may be constructed from four overlapping 3:5:7 chords, for example, V, II, VI, and IV, though different chords may be chosen to produce a similar scale:[9]

(5/3) (7/5)
V  IX  III
|
III VII I
|
VI I IV
|
IV VIII II


## Bohlen–Pierce temperament

"Chromatic circle" for the Bohlen–Pierce scale, with the third mode of the Lambda scale marked.[1]

Bohlen originally expressed the BP scale in both just intonation and equal temperament. The tempered form, which divides the tritave into thirteen equal steps, has become the most popular form. Each step is \sqrt [13]{3} = 3^{1/13} = 1.08818\ldots above the next, or 1200\log_{2}{\left(3^{1/13}\right)} = 146.3\ldots cents per step. The octave is divided into a fractional number of steps. Twelve equally tempered steps per octave are used in 12-tet. The Bohlen–Pierce scale could be described as 8.202087-tet, because a full octave (1200 cents), divided by 146.3... cents per step, gives 8.202087 steps per octave.

Dividing the tritave into 13 equal steps tempers out, or reduces to a unison, both of the intervals 245/243 (about 14 cents, sometimes called the minor Bohlen–Pierce diesis) and 3125/3087 (about 21 cents, sometimes called the major Bohlen–Pierce diesis) in the same way that dividing the octave into 12 equal steps reduces both 81/80 (syntonic comma) and 128/125 (5-limit limma) to a unison. A 7-limit linear temperament tempers out both of these intervals; the resulting Bohlen–Pierce temperament no longer has anything to do with tritave equivalences or non-octave scales, beyond the fact that it is well adapted to using them. A tuning of 41 equal steps to the octave (1200/41 = 29.27 cents per step) would be quite logical for this temperament. In such a tuning, a tempered perfect twelfth (1902.4 cents, about a half cent larger than a just twelfth) is divided into 65 equal steps, resulting in a seeming paradox: Taking every fifth degree of this octave-based scale yields an excellent approximation to the non-octave-based equally tempered BP scale. Furthermore, an interval of five such steps generates (octave-based) MOSes with 8, 9, or 17 notes, and the 8-note scale (comprising degrees 0, 5, 10, 15, 20, 25, 30, and 35 of the 41-equal scale) could be considered the octave-equivalent version of the Bohlen–Pierce scale.

## Intervals and scale diagrams

The following are the thirteen notes in the scale (cents rounded to nearest whole number):

Justly tuned
 Interval (cents) 133 169 133 148 154 147 134 147 154 148 133 169 133 Note name C D♭ D E F G♭ G H J♭ J A B♭ B C Note (cents) 0 133 302 435 583 737 884 1018 1165 1319 1467 1600 1769 1902
Equal-tempered
 Interval (cents) 146 146 146 146 146 146 146 146 146 146 146 146 146 Note name C C♯/D♭ D E F F♯/G♭ G H H♯/J♭ J A A♯/B♭ B C Note (cents) 0 146 293 439 585 732 878 1024 1170 1317 1463 1609 1756 1902

Steps EQ interval Cents in EQ Just intonation interval Traditional name Cents in just intonation Difference
0 3^\frac{0}{13} = 1.00 0.00 \begin{matrix} \frac{1}{1} \end{matrix} = 1.00 Unison 0.00 0.00
1 3^\frac{1}{13} = 1.09 146.30 \begin{matrix} \frac{27}{25} \end{matrix} = 1.08 Great limma 133.24 13.06
2 3^\frac{2}{13} = 1.18 292.61 \begin{matrix} \frac{25}{21} \end{matrix} = 1.19 Quasi-tempered minor third 301.85 -9.24
3 3^\frac{3}{13} = 1.29 438.91 \begin{matrix} \frac{9}{7} \end{matrix} = 1.29 Septimal major third 435.08 3.83
4 3^\frac{4}{13} = 1.40 585.22 \begin{matrix} \frac{7}{5} \end{matrix} = 1.4 Lesser septimal tritone 582.51 2.71
5 3^\frac{5}{13} = 1.53 731.52 \begin{matrix} \frac{75}{49} \end{matrix} = 1.53 BP fifth 736.93 -5.41
6 3^\frac{6}{13} = 1.66 877.83 \begin{matrix} \frac{5}{3} \end{matrix} = 1.67 Just major sixth 884.36 -6.53
7 3^\frac{7}{13} = 1.81 1024.13 \begin{matrix} \frac{9}{5} \end{matrix} = 1.8 Greater just minor seventh 1017.60 6.53
8 3^\frac{8}{13} = 1.97 1170.44 \begin{matrix} \frac{49}{25} \end{matrix} = 1.96 BP eighth 1165.02 5.42
9 3^\frac{9}{13} = 2.14 1316.74 \begin{matrix} \frac{15}{7} \end{matrix} = 2.14 Septimal minor ninth 1319.44 -2.70
10 3^\frac{10}{13} = 2.33 1463.05 \begin{matrix} \frac{7}{3} \end{matrix} = 2.33 Septimal minimal tenth 1466.87 -3.82
11 3^\frac{11}{13} = 2.53 1609.35 \begin{matrix} \frac{63}{25} \end{matrix} = 2.52 Quasi-tempered major tenth 1600.11 9.24
12 3^\frac{12}{13} = 2.76 1755.66 \begin{matrix} \frac{25}{9} \end{matrix} = 2.78 Classic augmented eleventh 1768.72 -13.06
13 3^\frac{13}{13} = 3.00 1901.96 \begin{matrix} \frac{3}{1} \end{matrix} = 3.00 Just twelfth, "Tritave" 1901.96 0.00

## Music and composition

What does music using a Bohlen–Pierce scale sound like, aesthetically? Dave Benson suggests it helps to use only sounds with only odd harmonics, including clarinets or synthesized tones, but argues that because "some of the intervals sound a bit like intervals in [the more familiar] twelve-tone scale, but badly out of tune," the average listener will continually feel "that something isn't quite right," due to social conditioning.[10]

Mathews and Pierce conclude that clear and memorable melodies may be composed in the BP scale, that "counterpoint sounds all right," and that "chordal passages sound like harmony," presumably meaning progression, "but without any great tension or sense of resolution."[11] In their 1989 study of consonance judgment, both intervals of the five chords rated most consonant by trained musicians are approximately diatonic intervals, suggesting that their training influenced their selection and that similar experience with the BP scale would similarly influence their choices.[8]

Compositions using the Bohlen–Pierce scale include "Purity", the first movement of

• Bohlen–Pierce Scale Research by Elaine Walker
• Bohlen–Pierce clarinets by Stephen Fox
• The Bohlen–Pierce Site: Web place of an alternative harmonic scale
• Kees van Prooijen's BP page
• song in Bohlen Pierce Scale
• Bohlen–Pierce symposium
• "Bohlen–Pierce Scale Symposium, Boston 2010" [playlist], YouTube.com.