Chord from just Bohlen–Pierce scale: CGA, 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 octaverepeating 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 octaverepeating 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

External links 10
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 equaltempered BP semitones ( ) on bottom and an interval of 4 equaltempered 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

C

D

E

F

G

H

J

A

B

C

Degree











Ratio

1/1

25/21

9/7

7/5

5/3

9/5

15/7

7/3

25/9

3/1

Cents

0

301.85

435.08

582.51

884.36

1017.60

1319.44

1466.87

1768.72

1901.96

Midi











Step

Name


T

s

S

T

s

T

S

T

s


Ratio


25/21

27/25

49/45

25/21

27/25

25/21

49/45

25/21

27/25


Cents


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 12tet. The Bohlen–Pierce scale could be described as 8.202087tet, 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 (5limit limma) to a unison. A 7limit linear temperament tempers out both of these intervals; the resulting Bohlen–Pierce temperament no longer has anything to do with tritave equivalences or nonoctave 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 octavebased scale yields an excellent approximation to the nonoctavebased equally tempered BP scale. Furthermore, an interval of five such steps generates (octavebased) MOSes with 8, 9, or 17 notes, and the 8note scale (comprising degrees 0, 5, 10, 15, 20, 25, 30, and 35 of the 41equal scale) could be considered the octaveequivalent 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

Equaltempered
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

Quasitempered 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

Quasitempered 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] twelvetone 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


Main Western



Types



Name



Ethnic origin



Modes



Number of tones





Composers




Tunings
& scales



Concepts &
techniques



Groups &
publications



Compositions



Other topics




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.
External links

^ ^{a} ^{b} Pierce, John R. (2001). "Consonance and scales". In Cook, Perry R. Music, Cognition, and Computerized Sound: An Introduction to Psychoacoustics. MIT Press. p. 183.

^ Bohlen, Heinz (1978). "13 Tonstufen in der Duodezime". Acoustica (in Deutsch) (Stuttgart: S. Hirzel Verlag) 39 (2): 76–86. Retrieved 27 November 2012.

^ Prooijen, Kees van (1978). "A Theory of EqualTempered Scales". Interface 7: 45–56.

^ Mathews, M.V.; Roberts, L.A.; Pierce, J.R. (1984). "Four new scales based on nonsuccessiveintegerratio chords".

^ Mathews, Max V.; Pierce, John R. (1989). "The Bohlen–Pierce Scale". In Mathews, Max V.; Pierce, John R. Current Directions in Computer Music Research. MIT Press. p. 167.

^ Mathews; Pierce (1989). pp. 165–66.

^ ^{a} ^{b} Mathews; Pierce (1989). p. 169.

^ ^{a} ^{b} Mathews; Pierce (1989). p. 171.

^ Mathews; Pierce (1989). p. 170.

^ Benson, Dave. "Musical scales and the Baker’s Dozen". Musik og Matematik. 28/06: 16.

^ Mathews; Pierce (1989). p. 172.

^ Thrall, Michael Voyne (Summer 1997). "Synthèse 96: The 26th International Festival of Electroacoustic Music". Computer Music Journal 21 (2): 90–92 [91].

^ "John Pierce (19102002)". Computer Music Journal. 26, No. 4 (Languages and Environments for Computer Music): 6–7. Winter 2002.

^ d'Escrivan, Julio (2007).

^ Benson, Dave (2006). Music: A Mathematical Offering. p. 237.

^ "Concerts". BohlenPierceConference.org. Retrieved 27 November 2012.

^ Bohlen (1978). footnote 26, page 84.

^ "Other Unusual Scales". The Bohlen–Pierce Site. Retrieved 27 November 2012. Cites: Moreno, Enrique Ignacio (Dec 1995). "Embedding Equal Pitch Spaces and The Question of Expanded Chromas: An Experimental Approach". Dissertation (Stanford University): 12–22.

^ "Other Unusual Scales", The Bohlen–Pierce Site. Retrieved 27 November 2012. Cites: Bohlen (1978). pp. 76–86.

^ Bohlen, Heinz. "An 833 Cents Scale". The Bohlen–Pierce Site. Retrieved 27 November 2012.

^ "BP Scale Structures". The Bohlen–Pierce Site. Retrieved 27 November 2012.

^

^
Sources
See the Delta scale and Gamma scale, also nonoctave repeating.
Alternate scales may be specified by indicating the size of equal tempered steps, for example Wendy Carlos' 78 cent alpha scale and 63.8 cent beta scale, and Gary Morrison's 88 cent scale (13.64 steps per octave or 14 per 1232 cent stretched octave).^{[22]} This gives the alpha scale 15.39 steps per octave and the beta scale 18.75 steps per octave.^{[23]}
An expansion of the Bohlen–Pierce tritave from 13 equal steps to 39 equal steps, proposed by Paul Erlich, gives additional odd harmonics. The 13step scale hits the odd harmonics 3/1; 5/3, 7/3; 7/5, 9/5; 9/7, and 15/7; while the 39step scale includes all of those and many more (11/5, 13/5; 11/7, 13/7; 11/9, 13/9; 13/11, 15/11, 21/11, 25/11, 27/11; 15/13, 21/13, 25/13, 27/13, 33/13, and 35/13), while still missing almost all of the even harmonics (including 2/1; 3/2, 5/2; 4/3, 8/3; 6/5, 8/5; 9/8, 11/8, 13/8, and 15/8). The size of this scale is about 25 equal steps to a ratio slightly larger than an octave, so each of the 39 equal steps is slightly smaller than half of one of the 12 equal steps of the standard scale.^{[21]}
Other nonoctave tunings investigated by Bohlen^{[17]} include twelve steps in the tritave, named A12 by Enrique Moreno ^{[18]} and based on the 4:7:10 chord Play , seven steps in the octave (7tet) or similar 11 steps in the tritave, and eight steps in the octave, based on 5:7:9 Play and of which only the just version would be used.^{[19]} The Bohlen 833 cents scale is based on the Fibonacci sequence, although it was created from combination tones, and contains a complex network of harmonic relations due to the inclusion of coinciding harmonics of stacked 833 cent intervals. For example, "step 10 turns out to be identical with the octave (1200 cents) to the base tone, at the same time featuring the Golden Ratio to step 3".^{[20]}
Other unusual tunings or scales
A first Bohlen–Pierce symposium took place in Boston on March 7 to 9, 2010, produced by composer Paul Erlich, Ron Sword, Julia Werntz, Larry Polansky, Manfred Stahnke, Stephen Fox, Elaine Walker, Todd Harrop, Gayle Young, Johannes Kretz, Arturo Grolimund, Kevin Foster, presented 20 papers on history and properties of the Bohlen–Pierce scale, performed more than 40 compositions in the novel system and introduced several new musical instruments. Performers included German musicians NoraLouise Müller and Ákos Hoffman on Bohlen–Pierce clarinets and Arturo Grolimund on Bohlen–Pierce pan flute as well as Canadian ensemble tranSpectra, and US American xenharmonic band ZIA, led by Elaine Walker.
Symposium
^{[16]} (2011)).Greater Good, and Love Song (1991), Stick Men (Elaine Walker As well as ^{[15]}^{[14]}).Splat (1994) & Frog à la Pêche Also Charles Carpenter ([13]
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