Spectral music often features microtones, but it is not per se microtonal music. Rather, microtones are used when they are necessary to approximate spectral models with enough precision.1 As a keyboardist, Pirro did not have access to an instrument that could accommodate the kind of spectral models he wanted to use in Stretch. Keyboards are traditionally chromatic instruments. They do not have the microtonal flexibility that his experiments with spectral distortion required.
This led Pirro to two strands of organological research:
The object was to build new instruments or, rather, to create new configurations of software patches and hardware interfaces that would afford the musical expression of Pirro’s chosen spectralist framework. Designing instruments like that is a process akin to experimental design or, as Smith and Dean call it, “research-led practice.” Pirro constantly put the work of programming software patches and interfaces to the test in his practice and adapted his designs accordingly.
Pirro’s first experiments with this dynamically tuned synthesizer include the piece "Someday I will shake your hand good-bye", recorded in collaboration with Italian vocalist Elisabetta Maulo, as well as a solo performance at the 3rd Conference of the International Network of Artistic Research in Jazz (February 23-25, 2023, Jam Music Lab University, Vienna).
While researching the stretching and compressing of spectra, Pirro felt the need to gauge the creative potential of these techniques in his practice. He wanted to hear and feel what the sonic effect of such spectral deformations would be, and to experiment with these sounds in improvisation.
His first experimental idea was to design an instrument with a dynamic tuning system that could be changed while performing. In order to do so, Pirro designed a software synthesizer controlled by a piano keyboard and a physical knob.
The piano keys are mapped onto a linear series of frequencies, and the knob controls the slope of the mapping (the amount of “spectral stretch”). This way, for certain knob values, the keys correspond to the partials of the natural overtone series. For other values, they correspond to the partials of stretched or compressed versions of this series.
In these experiments, Pirro noticed that his dynamically tuning keyboard missed elements of what he, in his practice, needed from an instrument. Chief amongst them was the possibility to play “wrong” notes, notes that did not belong to the harmonies he programmed. He likens it to the sensation of playing through autotune software. Initially, this allowed him to acquaint himself with the kind of harmonies the keyboard proposed. He developed a “feel” for the effect of the tuning knob and began to look for specific harmonies.
On the flip side, never being able to play outside the harmony caused Pirro to think less about the exact notes he was playing. In the end, it was not the keyboard, but the tuning knob that became the heart of the instrument, and the focus of his interaction with it. The instrument became a harmony selection knob with a keyboard accessory. While it gave rise to interesting experiments, Pirro felt that it narrowed the scope of his decision making too much to commit to it for the long term.
These considerations led Pirro to look for an entirely different way of integrating spectral techniques and microtonal playing in his performances. Instead of using an instrument that is “aware” of the spectral model in use, he decided to bring back this responsibility to himself, to the player. The traditional piano did not provide a sufficiently precise approximation of the pitches resulting from the spectral calculations, so he had to introduce an instrument capable of microtonal intonation. That instrument could then be used as a complement to the piano. Pirro chose to work with a digital controller called the LinnStrument.2
The LinnStrument is a digital controller that uses MIDI Polyphonic Expression (MPE), a communication protocol between electronic instruments that allows control of pitch, timbre, and other expressive elements on a per-note basis. Paired with a synthesizer that supports MPE, the LinnStrument can play up to 15 notes simultaneously. What is more, it is capable of sending MIDI pitch bend signals for each individual voice, which allows the player to microtonally control each pitch.
The layout of the LinnStrument does not resemble so much a piano keyboard as it does a fretted string instrument. Its keyboard is a continuous surface divided in a grid 8 rows of 25 note pads. Each row can be thought as the equivalent of a string on a fretted string instrument, but on the LinnStrument a simple pressure of a pad is enough to trigger a note, meaning that it is possible to play more than one note on the same ‘string’.
Since the LinnStrument is set up for more traditional diatonic music, Pirro had to thoroughly reconfigure it to fit his needs.3 In its final configuration each virtual “string” of the LinnStrument was an augmented fourth apart. Each point on a string was a different pitch, and to help navigate these microtonal continua Pirro highlighted the location of every C (red), E (white), and Ab (blue).
This is the LinnStrument configuration that Pirro uses for most of his playing. However, for Stretch, Pirro decided to design a specific arrangement of the LED lights that would provide a visual cue for the pitch reservoirs of each spectrum. This led to the light configuration shown in the picture below, that takes advantage of the fact that, like on a fretboard, the same pitch areas are present in more than one region of the LinnStrument. This way, the green area corresponds to the spectra with 0% and 4% of deformation, the purple area to 7% and 8%, and the blue/orange area to 13% to 17%.
Pirro not only reconfigured the LinnStrument; the LinnStrument also "reconfigured" its player. It forced a different approach with its challenging and unfamiliar keyboard layout, and by letting the player himself tune to the microtonal demands of spectral harmonies. Added to that, Pirro had only two years to figure out how to become a functional professional on his new instrument, and he had to do it without methods or outside help. Out of this pressure cooker emerged a new idiolect. It was marked by the avoidance of fast runs, in favor of carefully positioned tones that flesh out and complement spectral harmonies. To enhance spectral fusion, Pirro opted for a synth sound without a sharp attack and with a rather sinusoidal, flute-like waveform. The LinnStrument came to occupy a liminal zone between harmony and melody, rarely taking the fore-, or receding into the background.