David-Jubal
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This article or section contains multiple idiosyncratic terms. Such terms are used by only a few people and are not regularly used within the community.
Terms: The terms David-Jubal tuning, David's chord, Jubal's scale, harmonic strength, David-John tuning and David-John scale were coined by John O'Sullivan in the mid 2020s and are not so far widely known to other microtonalists. |
David-Jubal tuning is a musical framework invented by John O'Sullivan in the 2020s. It is a type of just intonation. It consists of the use of Jubal's scale as its pitch gamut, and David's chord as its primary sonority. (For contrast, compare to most 21st century Western music which uses the 12edo chromatic scale as its pitch gamut and the (tempered) major and minor triads as its primary sonorities).
O'Sullivan describes David-Jubal tuning, the reasoning behind it, and practical instructions for fretting a guitar or similar instrument, on his website:
Theory
Harmonic strength
Harmonic strength is a term invented by O'Sullivan to describe a measure of the strength of a just sonority. It equals 2/n + 2/d (where n/d is the simplified interval ratio).
O'Sullivan considers a good tuning to be a tuning with as many intervals as possible with a harmonic strength of 0.5 or higher, and as few intervals as possible with a harmonic strength of 0.25 or higher.
The goal of David-Jubal tuning is to be as 'good' as possible by those criteria.
David's chord
David's chord is the name O'Sullivan coined for the just intonation chord 1:2:3:4:5:7. This chord is derived by starting with the first 9 tones of the harmonic series and removing all instances of the intervals O'Sullivan considers to be dissonances: 6/5, 7/6, 8/7 and 9/8.
David's chord consists of four pitch classes: E, B, G# and D when tuned to E.
O'Sullivan discourages the use of minor triads in music build upon David's chord, considering them "destructive" to the harmonic affect of the chord. When retuning 12edo music to David-Jubal tuning, O'Sullivan recommends replacing minor triads with power chords (2:3:4).
O'Sullivan considers 2:3:4:5:7 to be an acceptable substitute for David's chord, for practical use on instruments, given the difficulty of including an entire additional octave.
Jubal's scale
Jubal's scale is the just intonation scale 8:9:10:10.666...:12:13.333...:14:15:16:18:20.
Its intervals are: 1/1, 9/8, 7/6, 5/4, 4/3, 3/2, 5/3, 7/4, 15/8, 2/1.
O'Sullivan replaced harmonics 11 and 13 in the scale because the intervals between them and the other scale degrees do not have high 'harmonic strength'.
Scala file
! jubal.scl ! Jubal's scale, John O'Sullivan, key of E 10 ! 9/8 7/6 5/4 4/3 3/2 5/3 7/4 15/8 2/1
David-John tuning
David-John tuning is an analogous concept to David-Jubal tuning but using the David-John scale (8:9:10:11:12:13:14:15:16:18:20) instead of Jubal's scale.
Relationship to other scales and concepts
Within the framework of otonal and utonal analysis, David-Jubal tuning is a strongly otonal tuning, which deliberately avoids utonality.
The intervals O'Sullivan removed from David's chord are all the superparticular intervals smaller than 5/4.
Jubal's scale bears a slight resemblance to Paul Erlich's 'pentachordal decatonic scale' (the pajara[10] scale of 22edo).
Jubal's scale is a subset of 24afdo (the 24th mode of the harmonic series).
The David-John scale is harmonic series segment 8::20, and it is a subset of 8afdo (the 8th mode of the harmonic series). In fact it contains every pitch class from 8afdo at least once and sometimes twice. This makes the David-John scale an over-2 scale within primodality theory.
Jubal's scale is a 7-limit just intonation scale and the David-John scale is a 13-limit just intonation scale.
Music
David-Jubal tuning
On his YouTube channel "@johnsmusic7", O'Sullivan has compiled the following playlist of 14 musical examples that use David-Jubal tuning: