Eagle 53

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

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. ("Strength" according to the metric 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 metric 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.

Though it used a completely different methodology than a well temperament, the philosophy behind Eagle 53 was similar to one. It is not a well temperament, but it achieves many similar aims to one.

Relationship to other scales

Eagle 53 is a subset of 53edo.

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

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.

Scala file

! eagle53.scl
!
 Eagle 53, John O'Sullivan, key of E
 12
!
 113.208
 203.774
 316.981
 384.906
 498.113
 588.679
 701.887
 815.094
 883.019
 1018.868
 1086.792
 1200.000

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

Music

• Taking Flight - Xotla (2019)

Further reading

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