David Løberg Code Groven.Max: School of Music Western Michigan University Kalamazoo, MI 49008 USA An Adaptive Tuning [email protected] System for MIDI Pianos Groven.Max is a real-time program for mapping a renstemningsautomat, an electronic interface be- performance on a standard keyboard instrument to tween the manual and the pipes with a kind of arti- a nonstandard dynamic tuning system. It was origi- ficial intelligence that automatically adjusts the nally conceived for use with acoustic MIDI pianos, tuning dynamically during performance. This fea- but it is applicable to any tunable instrument that ture overcomes the historic limitation of the stan- accepts MIDI input. Written as a patch in the MIDI dard piano keyboard by allowing free modulation programming environment Max (available from while still preserving just-tuned intervals in www.cycling74.com), the adaptive tuning logic is all keys. modeled after a system developed by Norwegian Keyboard tunings are compromises arising from composer Eivind Groven as part of a series of just the intersection of multiple—sometimes oppos- intonation keyboard instruments begun in the ing—influences: acoustic ideals, harmonic flexibil- 1930s (Groven 1968). The patch was first used as ity, and physical constraints (to name but three). part of the Groven Piano, a digital network of Ya- Using a standard twelve-key piano keyboard, the maha Disklavier pianos, which premiered in Oslo, historical problem has been that any fixed tuning Norway, as part of the Groven Centennial in 2001 in just intonation (i.e., with acoustically pure tri- (see Figure 1). The present version of Groven.Max ads) will be limited to essentially one key. Temper- accepts input via MIDI keyboards or a MIDI file. ing provided a wider range of available keys, but at This input is analyzed and rerouted to three sepa- the expense of the purity of the intervals. Mechani- rate instruments (real or virtual) tuned to produce a cal solutions involving keyboards with more keys 36-tone scale. In performance, one can either select per octave, such as Giovanni Battista Doni’s cem- fixed, twelve-note scales from among the 36 avail- balo pentarmonico from 1635 with 68 keys per oc- able tones, or use the adaptive tuning feature for tave, or Julian Carrillo’s sixteenth-tone piano from dynamically selecting just intervals while modulat- the mid 20th century with 96 keys per octave, re- ing keys. quired performers to learn a new, and sometimes awkward, playing technique, and thus never gained Background widespread popularity. A more comprehensive overview of microtonal keyboards can be found in Keislar (1987). Eivind Groven and His Renstemt Organ Groven sought a solution that would require only a standard keyboard (and keyboardist), yet use The Norwegian composer and ethnomusicologist a larger number of pitches per octave. At any given Eivind Groven (1901–1977) spent much of his life time, each individual key on the manual is con- striving to bridge the gap between his native folk nected to one of three possible pipes, each tuned to music and Western classical music. His most no- a slightly different frequency. One can either pre- ticeable accomplishment in this regard was the select a fixed set of twelve pipes for the duration of construction of the 36-tone renstemt, or pure- a performance or engage the adaptive tuning fea- tuned, pipe organ for playing both traditional folk ture or the renstemningsautomat for dynamic and standard classical repertoire. The scale is based tuning. on just intonation, a tuning system using acousti- Inspired by telephony, Groven built his first ren- cally pure intervals from the harmonic series. The stemningsautomat most remarkable feature of the organ is Groven’s using automatic telephone switchboard relays that, in essence, routed calls Computer Music Journal, 26:2, pp. 50–61, Summer 2002 from the organ manual to the bank of pipes (see ᭧ 2002 Massachusetts Institute of Technology. Figure 2). 50 Computer Music Journal Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/014892602760137176 by guest on 30 September 2021 Figure 1. World Premie`re Figure 2. Eivind Groven of the Groven Piano, 19 soldering relays in his April 2001, Oslo, Norway automatic tuning device. (Disklaviers courtesy of Yamaha Scandinavia). This was cutting-edge technology in 1939, when this project was begun, as the automatic switch- board had not been in widespread use in Norway for very many years. In the 1960s, the closet-sized switchboard interface was replaced by a smaller de- vice using electronic transistors, built by Bjørn Raad at the Central Institute for Industrial Re- search in Oslo, Norway. Although showing signs of age, this interface is still in operation today and services both the pipe organ and 36-tone electronic organ built in 1965. These organs, along with a 43-tone electronic organ (built in 1965 but no longer in operation), are housed at the Eivind Groven Institute for Just Intonation on the out- skirts of Oslo, Norway. Further background infor- mation about Groven’s work can be found in Code (2001; in press), Groven (1927, 1934, 1935, 1948a, 1948b, 1955, 1968, 1971), and Lysdahl (1997). More recently, interest in Groven’s work has led to the development of computer programs that simulate aspects of his renstemningsautomat (but not in real-time), such as those written by Jørn Ar- vidsen (1982) and Lars Frandsen (1995). Knut-Einar Skaarberg (1995) has adapted Groven’s tuning logic into a program that controls the MIDI pitch-bend function of an electronic synthesizer in perfor- mance (with polyphonic textures using multiple MIDI channels). Code 51 Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/014892602760137176 by guest on 30 September 2021 Groven.Max was originally developed for use the other to select a tuning. (A similar concept was with custom-tuned pianos, but it can also be used employed in Cooper’s 1998 software RealTime with synthesizers or other MIDI-controlled in- Tuner 1.2.) When a tuning key was pressed, a set of struments. There is currently a project underway relays actuated electromagnets to stretch or relax with NoTAM (Norwegian Network for Technol- each string individually in accordance with a given ogy, Acoustics, and Music) to renovate Groven’s scheme. While the piano was not supposed to pipe organ and replace the current electronic inter- change tuning by itself, it could (in theory) be in- face with a computer-operated system using stantly re-tuned during performance by pressing an- Groven.Max. While the work of Arvidsen , Frand- other of the 23 available tuning keys. The design sen, and Skaarberg represents the first transferences was never fully tested, as Groven was unable to ob- of Groven’s logic from hardware to software, there tain funding to build a prototype piano and turned are of course numerous other precursors to his attention to organ instead. Groven.Max within the field of automatic (and In 2001, his original goal of creating a variably- semi-automatic) tuning systems. Other adaptive tuned acoustic piano was finally realized with the tuning systems and software for various electronic world premiere of the Groven Piano. Named in instruments not related to Groven’s work have also honor of Groven’s hundredth birthday, the Groven been developed since his death. See, for example, piano comprises a network of three acoustic pi- Cooper’s RealTime Tuner (available from anos, a control keyboard, and a computer interface socrates.berkeley.edu/ϳwcooper/realtimetuner running Groven.Max software. Like Groven’s or- .html), Gannon’s and Weyler’s Justonic (available gan, the pianist plays upon a standard keyboard from www.justonic.com), as well as Denckla that, instead of making its own sound, sends a (1997), Polansky (1987), Scholz (1986), and Steck MIDI signal to Groven.Max. Three Disklavier pi- and Roush (1998). It is beyond the scope of the anos, donated for the premiere by Yamaha Scandi- present article, however, to provide a comprehen- navia, were each tuned differently, thus providing sive survey of such work. 36 strings per octave to match the organ’s 36 pipes. Groven himself cites as a precedent John Hay- Thus, unlike Skaarberg’s program, Groven.Max wood Compton’s 1933 British patent describing an does not send pitch-bend or system-exclusive com- mands to retune the instruments dynamically, but ‘‘enharmonic’’ organ similar in operation to Harold simply reroutes the MIDI signal for each note Waage’s more recent ‘‘intelligent keyboard’’ (1988). played to the piano with the desired tuning for that Compton’s organ featured an extra set of equal- pitch (similar in function to Groven’s renstemning- tempered pitches 14 cents below the first that sautomat). The premiere took place on 19 April would be automatically inserted when necessary to 2001 at Norges musikkhøgskole (The Norwegian produce more favorably-tuned thirds and sixths. Academy of Music) in Oslo, Norway, with support from Yamaha Scandinavia, Norsk Kulturra˚d, the Ei- vind Groven Institute for Just Intonation, the US- The Groven Piano Norway Fulbright Foundation, and the University of Oslo. (Photographs and audio samples of the pre- Groven’s first attempts to solve the keyboard’s miere are available online at vms.cc.wmich.edu/ ‘‘tuning problem’’ actually did not use the organ, ϳcode/groven/konsert.html.) The concert, which but rather the piano, and they involved an auto- was intended to demonstrate the versatility of the mated, but not adaptive, re-tuning system. In the instrument, featured classical, jazz, and folk music mid 1930s, he received patents in several countries with both solo piano and ensemble pieces. The for a variable tuning device for piano (e.g., British North American premiere of the Groven Piano is patent No. 422,669; 1935).