The Sauter Omega includes an extra register in the form of coloured lines on the soundboard. These lines indicate where to touch the strings to get the first, second and third order harmonics. If you touch a string at the point of the lines and press the key or pluck the string, you hear the correspondent harmonics and partials.
- The first order harmonic is available across the keyboard, from A0 to C8, indicated by the black line furthest from the dampers.
- The second order harmonic from A0 to G2, and from D3 to A4, indicated by the red line. The gap from G#2 to C#3 is due to the fact that these strings cross under the bass strings and are therefore not accessible.
- The third order harmonic from A0 to G2, indicated by the blue line closest to the dampers in the bass notes.
The damper of every white key is etched with a white bar. The picture below from the Sauter web site shows the extra register lines more clearly.
I doubt that I (and probably 99% of pianists) would ever use the extra register, but it is interesting nonetheless that Sauter made the Omega for prepared piano compositions. It seems that grand pianos around the 7-ft size are ideal for prepared piano. Full-sized concert grands are too long for the pianist to reach the harmonic points while standing at the keyboard.
Here is the track “I’m Broken” from the album Bitter and the Sweet, by the Cécile Verny Quartet. It demonstrates the use of the Omega’s extra register.