The island tetrad under octave reduction consists of three 15/13 intervals followed by a 13/10, which closes on the octave since the island comma, 676/675, is tempered out; in other words an island tempered version of
Contained within it are a barbados triad,
- 1-13/10-3/2, with steps 13/10-15/13-4/3,
- 1-15/13-3/2, with steps 15/13-13/10-4/3,
and an island triad,
- 1-15/13-4/3, with steps 15/13-15/13-3/2,
which in another position is the 1-3/2-26/15 chord.
Another island tetrad of interest is a 26/15 over a major triad,
- 1-5/4-3/2-26/15, with steps 5/4-6/5-15/13-15/13,
and its inversion,
- 1-6/5-3/2-26/15, with steps 6/5-5/4-15/13-15/13.