 Photo by Will Gullette |
| Twilight Music by Cris Forster Cris Forster, Just Keys |
| Good-Bye Music by Cris Forster Isabelle Jotterand, Just Keys |
| Farewell Music by Cris Forster Isabelle Jotterand, Just Keys |
| Far Away Music by Cris Forster Cris Forster, Just Keys |
| In the Park Music by Cris Forster Joseph Rogers, Just Keys |
| The Letter Music by Cris Forster Cris Forster, Just Keys |
| Blue Nights Music by Cris Forster David Boyden, Bass Canon Heidi Forster, Glassdance Isabelle Jotterand, Just Keys Benjamin Koscielak, Bass Marimba |
| Modified: | San Francisco, California. • 1990. Replaced original strings with thin wound strings and thin plain strings. • 2001. Inlaid all keys with Lexan-covered color-coded ratio labels. • 2007. Installed a set of German Wurzen Felt hammers. | |
| Range: | Eb1 (8/5) 39.2 cps ← G1 (1/1) 49.0 cps → C8 (4/3) 4181.3 cps | |
| Tuning: | Just Intonation. |
Just Keys is a medium upright acoustic piano. To minimize the devastating effects of inharmonicity, in 1990, I restrung this instrument three times — with thin plain steel strings in the treble and thin wound copper strings in the bass — and retuned it four times to various scales in just intonation. To further counteract aural perceptions of inharmonicity, the new Wurzen Felt hammers give this instrument a rich and warm timbre.
The graphic above shows the complete keyboard, with Lexan-covered color-coded ratio labels, from the first key in the bass to the last key in the treble.
Note that the B-3 key identifies ratio 1/1, which is the fundamental frequency of the tuning. This key sounds G1 at 49.0 cps! Since the G-11 key normally produces this frequency, observe that I eliminated most of the tones that comprise the first octave of the standard piano. Consequently, the A-1 key now sounds frequency ratio 8/5, or a just major third, interval ratio 5/4, below 1/1, which is Eb1 at 39.2 cps; and the A#-2 key now sounds frequency ratio 16/9, or a just major second, interval ratio 9/8, below 1/1, which is F1 at 43.6 cps.
A 10-tone octave, ratios 1/1–2/1, exists from the B-3 key to the A-13 key (two keys with two dark blue labels); a 17-tone octave, ratios 2/1–4/1, from the A-13 key to the D-30 key (two keys with two dark blue labels); and another 17-tone octave, ratios 4/1–8/1, from the D-30 key to the G-47 key (two keys with two dark blue labels). From here, three consecutive 12-tone octaves, ratios 8/1–16/1, ratios 16/1–32/1, and ratios 32/1–64/1 span the distance from the G-47 key to the G-83 key. These 12-tone scales resemble the tuning of a conventional piano. Short string lengths, determined by the shape of the cast iron plate and the location of the treble bridge, severely restrict alternate tuning possibilities in the upper treble range.
