1/1 Journal of the Just Intonation Network vol 8 #2 jan 1994 p 12 footnotes are indicated by asterisk number as in example*1 copyright 2326w

The Enhanced Piano by Loren Rush, Janis Mattox, and Alfred Owens

The Enhanced Piano (TM) was developed at Good Sound Foundation's Skyline Studio in Woodside, California, where two pianos, tuned in Just Intonation, have been enhanced to increase their perceived resonance, sustaining, coloristic, and expressive capabilities. The enhanced piano is performed within A Virtual Acoustical Environment (TM)*1 (VAE (TM)) -- an electroacoustical performance-space enhancement system that creates the perceptual characteristics of a variety of acoustical environments in ordinary performance spaces. The VAE enables performers to hear and be heard as if they and their audience were actually in the "virtual" space. The Enhanced Piano and the VAE are effective for both recording and live performance in either the studio or the concert environment. An overview of this system is shown in Figure 1.

Although the authors have a long history in the musical application of Jest Intonation, our use of Just Intonation for the enhances piano is based on the pioneering work of La Monte Young*2, Terry Riley*3, and W.A. Mathieu*4.

The first public presentation of the enhanced piano took place at Good Sound Festival '92 at Fort Mason Center in San Francisco -- a series of seven concerts featuring over thirty Bay Area performers. Two recordings from this festival are available (The Good Sound Band '92*5 and GSQ '92*6). Early versions of the enhanced piano can be heard in Loren Rush's A Little Traveling Music*7, on the soundtrack for Book of Shadows, a video ballet by Janis Mattox*8, and in Numbers Racket, The Just Intonation Network Compilation Volume II*9, which contains excerpts from Book of Shadows.

ELectroacoustic Signal Processing A piano tuned in Just Intonation is characteristically more resonant than a piano tuned in equal temperament. With the enhanced piano, this natural resonance is increased by the application of digital signal processing.

The piano is fitted with a MIDI keyboard interface and foot pedals that control a digital audio processor and synthesizer that projects directly onto the underside of the sound board by means of a loudspeaker, providing the pianist with flexible and subtle control. The enhanced piano can be heard clearly on stage and in the audience in even the most delicate music, without sacrificing the richness and integrity of the natural piano tone, and without limiting the piano to those techniques that tend to serve projection better than they serve expression. These enhancements are particularly noticeable in the bass register, where even the best pianos tend to sound clangorous.

The MIDI interface transmits the pitch number, velocity, pressure, and attack and release characteristics of each piano key. This MIDI stream is received by a digital synthesizer that is tuned to within one cent of each of the piano pitches. The synthesizer produces tones that are a timbral match to the steady state of the piano tone.

The digital signal processor receives the signal from the synthesizer, from which it produces a very diffuse signal with no audible coloration. The loudspeaker under the piano transmits this signal through the air to the piano sound board and strings, at which point the piano sound board and strings, at which point the piano enhancement is complete. Extremely flexible, this system can be conformed to the musical needs of the moment with accuracy and ease by the pianist during performance.

The Enhanced Piano is placed on a "virtual stage," a component of the Virtual Acoustical Environment. The Sound Capture Module (TM) (Figure 2) receives the enhanced sound from the piano. This signal is transmitted to a digital signal processor where the simulation of the characteristics of the stage of a concert hall takes place. Loudspeakers surrounding the piano receive the signals from the signal processor and transmit them to the air, where they are combined with the sound from the enhanced piano and picked up again by the Sound Capture Module ... and so forth. As with the piano enhancement, the stage system is very flexible and can be tuned by the pianist in performance.

Sound Capture Module (SCM) The microphone capsule of the SCM first receives the direct sound, which is followed by the reflected sound from a diffusion matrix. This provides sound quality that is better approximation of the way the human ear/brain focuses on sound than can be obtained by a microphone alone. The diffuser also works as a noise baffle for the microphone and as a multidimensional focusing element.

The SCM neutralizes unwanted ceiling reflections, a great advantage when dealing with low ceilings. In a concert installation, the SCM is placed over the audience in order to include the full sound of the Virtual Acoustical Environment. It is then equalized to reject acoustical anomalies of the actual room that may be excited by, for example, loud drums.

The Sound Capture Module is the invention of Thomas L. Paddock, a member of the Good Sound Foundation Technical Committee and CEO of SRA Engineering, San Jose, California.

Tuning The two enhanced pianos at Good Sound Foundation's Skyline Studio are tuned in Just Intonation, a system that uses small number integer ratios to set the relationship between the pitches of the strings. There is evidence of tuning by small number ratios in ancient cultures of Arabia, China, Egypt, India, Greece, and Persia, and -- except for the music of Indonesia and some modern European classical music -- Just Intonation seems to have been the way of tuning, world-wide, for all time.

In Europe during the late 18th and early 19th centuries, instruments of fixed tuning such as keyboard and fretted instruments were treated to various tuning schemes to enable them to satisfy the European's growing fondness of modulation and intervallic equality. in time this became an apparent norm, so that today nearly all keyboard and fretted instruments tune to equal temperament. however, other instruments such as bowed strings, woodwinds and brass, continue to this day -- with the exception of the occasions in which they are supporting instruments of fixed pitch -- to tune to a floating constantly adjusting Just Intonation.

Method Each of the pianos is tuned to a subset of a 19-tone Just Intonation system with six common tones (shown in bold in Figure 3). One piano is tuned in a five-limit system, where the most complex tuned interval is the 5:4 major third; the other is tuned in a seven-limit system, where the most complex tuned interval is the 7:4 minor seventh. C(4) (middle C) is tuned in equal temperament from A(4) = 441 Hz. This results in a pitch distribution that, in relation to an equal tempered tuning based on A-440, had a balanced distribution of sharp and flat pitches, minimizing the amount of adjustment from equal temperament for the piano tuner and for instrumentalists performing with the pianos. In the seven-limit tuning, the C's from middle C down (C(1-4)) are tuned as described above and the C's from an octave above middle C and up (C(5-8) are tuned as a 7:4 minor seventh from D.

Harmonic Stretch Because of its high mass density, the piano string tends to have rod-like vibrational characteristics. The resulting inharmonicity is characterized by a sharpening of the string's upper partials in relation to the theoretical harmonic series (1:2:3:4:5:6:7...). In order to minimize this discrepancy, tuners have found it necessary to apply a stretch to the tuning of the octaves, with the bass becoming increasingly flat and the treble becoming increasingly sharp.

The common-practice method of stretching is to focus mainly on the relationship between the lower octave's second partial and the upper octave's fundamental. This produces relatively consonant octaves but leaves dissonances in the bass range between the string's upper partials and the strings in the "Mozart" octave, G(4) - G(5) (G above middle C to G above the staff), the piano's primary melodic range.

For the enhanced piano, we have developed what we call the harmonic stretch, in which each bass string is tuned to the best alignment of its partials to the Mozart octave. For example, in the seven-limit system C(2) (two octave below middle C) would be tuned so that partial numbers 6, 7, 8 and 10 are consonant with G, Bflat, C and E of the Mozart octave. The harmonic stretch gives the bass tone a true harmonic functionality that is much closer, for example, to the way a string quartet tunes than the usual piano tuning -- making it also a more natural tuning environment for orchestral instruments.

Wet Tuning The enhanced piano is also capable of variable wet tuning, the shimmer that results for the slight mistuning of unisons. Wet tuning is a feature of some accordion tunings, and a more extreme wet tuning is an essential feature of Balinese instruments. Using the piano's una corda feature, the ability to change the number of strings the hammer strikes, the unison strings are tuned so that in one position the hammer strikes only the exact unison strings, while in the other the mistuned strings are also struck. Since the una corda pedal can shift the hammers in a very gradual manner, this feature adds great expressive capability to the piano. For example, pure unisons can be used to start a phrase and the mistuning can be added gradually as the phrase intensifies.

References *1. Loren Rush, A Virtual Acoustical Environment. Good Sound Foundation report. 2995 Woodside Road #400, Woodside, CA 94062.

*2. La Monte Young, The Well-Tuned Piano. Gramavision 5CD 1808701-2.

*3. Terry Riley, The Harp of New Albion. Celestial Harmonies 2CD CEL 018/19.

*4. W.A. Mathieu, Lost Chords. In the Wind. Cold Mountain Music, 9195 Barnett Valley Road, Sebastopol, CA 95472.

*5. The Good Sound Band '92. Recorded in concert at Good Sound Festival '92 in San Francisco, this Just Intonation ensemble directed by Janis Mattox and Loren Rush performs new works and collaborations with Stuart Dempster, Susan Deihim, Mel Graves, George Marsh, John M. Grey, Jon A. English, Candace Natvig, Daniel Kobialka, Jennifer Wilsey, and Timothy White. Tuning design by Loren Rush and Alfred Owens. Piano tuning by Alfred Owens. Cassette or DAT available from The Just Intonation Store.

*6. GSQ '92. Recorded in concert at Good Sound Festival '92 in San Francisco. Features Loren Rush, enhanced pianos in Just Intonation, Mel Graves, contrabass, George Marsh, drumset and percussion, and Timothy White, sitar, performing Slow Blues in Five-Limit Tuning. 90 minutes. Tuning design by Loren Rush and Alfred Owens. Piano tuning by Alfred Owens. DAT available from the Just Intonation Store.

*7. Loren Rush, A Little Traveling Music; for piano in five-limit tuning, digital synthesis, cymbal and ocean. Dwight Peltzer, pianist. Tuning design by Loren Rush and Alfred Ownes. Piano tuning by Alfred Owens. Computer Music Currents 2, Wergo CD WER 2022-50.

*8. Janis Mattox, Book of Shadows; an award-winning erotic video ballet featuring dancers Marci Javril and Riccardo Morrison with a Just Intonation soundtrack performed by: Sussan Deihim, vocals; Stuart Dempster, garden hose and didjeridu; Jon English, contrabass; Mel Graves, contrabass; Kaniel Kobialka, violin; Pauline Oliveros accordion in Just Intonation; Loren Rush and Janis Mattox, enhanced pianos in Just Intonation; Timothy White, flute and soprano saxophone. Tuning design by Loren Rush and Alfred Owens. Piano tuning by Alfred Owens. VHS tape available from The Just Intonation Store.

*9. Janis Mattox, two excerpts for Book of Shadows featuring the enhanced pianos. Numbers Racket, The Just Intonation Network Compilation Volume II. Cassette tape available from The Just Intonation Store.


Loren Rush: Composer, pianist, acoustical systems designer, specialist in digital audio research. Served for twelve years as a founding director of Stanford University's Center for Computer Research in Music and Acoustics. Co-founder and chief executive officer of Good Sound Foundation (GSF). Recent GSF research has resulted in the development of The Enhanced Piano (TM) and The Virtual Acoustical Environment (TM) (VAE(TM)). The VAE was premiered at the Brooklyn Academy of Music's Majestic Theater in December in support of Njinga the Queen King.

Rush's compositions have been conducted by Pierre Boulez, Dennis Russell Davies, James DePriest, Lukas Foss, Eduardo Mata, Seiji Ozawa, Ferruccio Scaglia, Leonard Slatkin and Niklaus Wyss and the San Francisco Symphony, is the first orchestral composition to employ the artistic use of electroacoustical signal processing in performance. Song and Dance (1975), commissioned by Seiji Ozawa and the San Francisco Symphony, is the first orchestral composition to employ digital synthesis in performance. Currently composing Della Vita d'un Uomo for Thomas Buckner, baritone, and Joseph Kubera, enhanced piano in five-limit tuning -- to be premiered with an installation of the VAE in 1995 in New York.

Janis Mattox. Composer, pianist and film maker, Janis Mattox is a founder and co-director of Good Sound Foundation, a group of musicians, artists and technologists dedicated to revitalizing the experience of sound in live performance. She has created and produced works involving new music technologies, musicians, actors and dancers at Stanford University's Center for Computer Research in Music and Acoustics since 1978. Mattox' work incorporates archetypal dramatization, experimental sound and lighting design, film, video, and just tuning systems.

Alfred Owens. Composer, vocalist, piano technician; B.F.A. (music) New College of California. Ownes graduated from the Perkins Institute of Piano Technology in Cleveland, Ohio in 1977. Since then he has worked as a tuner and consultant on Just Intonation works for piano and accordion with composers such as La Monte Young, Terry Riley, Allaudin Mathieu, Loren Rush and Pauline Oliveros. He has also had formal music studies with several of these composers. In addition to specializing in alternative tuning systems, Alfred Owens has done conventional tuning for many recording studios and concert venues in the Bay Area. He currently writes and produces musical scores for film and media and performs with other local artists.

Typed by C. Vega 1-29-96