Eagle 53

Eagle 53 is a 12-tone tempered scale invented by John O'Sullivan. It is a subset of 53edo.

Scala file

! eagle53.scl
!
 Eagle 53, John O'Sullivan, key of E
 12
!
 113.2
 203.8
 317.0
 384.9
 498.1
 588.7
 701.9
 815.1
 883.0
 1018.9
 1086.8
 1200.0

Detempering

! eagleJI.scl
!
 Eagle 53 detempering, John O'Sullivan, key of E
 12
!
 16/15
 9/8
 6/5
 5/4
 4/3
 7/5
 3/2
 8/5
 5/3
 9/5
 5/8
 2/1

Conception

O'Sullivan designed Eagle 53 to meet the following criteria:

1. Every note between 1/1 and 2/1, when paired with both 1/1 and 2/1 must make a high strength or medium strength melodic interval. ("Strong" according to the criteria described in Eagle 53 Article (2017)).
2. The tuning must not have more than 12 notes per octave, so as to fit comfortably on small stringed instruments like ukeleles.
3. There must be at least one good chord on each of the twelve notes. ("Good" according to the criteria described in Eagle 53 Article (2017)).
4. These good chords must be playable on a fretted instrument such as a guitar.

The overall aim was to improve upon and replace 12edo, by making 12edo's consonances even more in-tune, at least in the most important keys, while also making available new exotic consonances and melodies which 12edo lacks.

Relationship to other scales

Eagle 53 is identical to Euler's Genus Diatonico-chromaticum and Ellis' Duodene, except that those used 45/32 instead of 7/5 in their just version.

This similarity is by coincidence and may simply speak to the fact that this is a useful and relatively simple scale that theorists are likely to land upon over and over, much like 2L 3s or like 53edo itself.

Music

• Taking Flight - Xotla (2019)

Further reading

• Eagle 53 Article - John O'Sullivan (2017)
• Eagle Tuning Facebook group
• johnsmusic7.com: O'Sullivan's website. Contains further material on Eagle 53 among other topics.