Chapter 4: Technical Implementation – piano+
4.5. Other Implemented Processes
4.5.1 Ring Modulation and Pitch Shifting
The piano+ also features a combined module of ring modulation and pitch shifting. Ring modulation has a long history within live electronic performances380 and is commercially available since the early 1960s by Bode and Buchla. The distinct bell-like quality of the effect remains compelling, particularly when mixed with other processes, where either the acoustic sound is ring-modulated, but the granulated tail is not, or vice versa. The control required is minimal, only carrier frequency and volume, although a serially placed filter has been employed to reduce lower frequencies as the process introduces sidebands to the partials which can thicken the result unnecessarily and cause feedback problems. This process is pitch related, so an ‘opposing’ quality was selected to allow a different characteristic and to increase the parameter space. An FFT based transposer381 was chosen allowing transpositions of -12 to 12 semitones. The parameters of the combined processes are assignable in the manner described in the previous section.
4.5.2. Filters
Filters are used in various forms in the processes designed for the piano+. Basic low- and high-pass filters are used to reduce problematic frequency areas and to treat the microphone inputs to reduce the chances of low feedback drones and reduce the sharpness of high pitched clicks which can occur in some processes. These filters have fixed settings that are only changed very occasionally and are therefore not considered as a performative tool here.
380 I.e. Stockhausen’s Mantra (1979). 381 Based on gizmo~ in Max/MSP.
Experimentation with different filters has shown the possibility of (ab-)using a fast- fixed-filter-bank (fffb~ in Max5). Exaggerated values for frequency (including the Nyquist area, i.e. 1 - 44100Hz), Q and gain enable digital glitchy, ‘bubbly’, and ‘airy’ alienations of the incoming signal. This process has mainly been controlled by a pair of sensors (often IR distance sensors) to determine the frequency of the 8 filter bands, one to set a pitch, the other to transpose. Depending on the bandwidth Q and gain settings, the audio output can vary extremely in volume, particularly if the settings lie on one of the main partials of the sound. A rigorous limiting method was implemented to tame this process, as it had caused several sudden, dangerously loud moments during studio sessions and performances alike. Furthermore these extremely filtered frequency bands are only used for a short time (determinable and randomisable by a parameter). This filter allows the manipulation of the already quite dominant onset or to disrupt the otherwise smoother decay of the sounds and forms the most obvious digital transformation available in the setup, as they clearly signify electroacoustic treatments, rather than more subtle subversions of the acoustic sound.
The filter and pitch modules are regarded as ‘processes on the vertical axis’382, as these modulate the acoustic sound within the same amplitude shape. The fffb~ filter module has some perceivable impact on the ‘horizontal axis’. The moment the individual filter bands open might be perceived as a distinct event383. Nevertheless, the process is always dependent on real-time input, even if it is near silence.
The fffb-filter implementation was initially developed to enhance the weaker partials in the piano spectrum. Audio analysis would set the pitch parameter while the performer would choose a transposition to allow the filter to tune into a specific harmonic of the note (under the assumption that the reading of the frequency was actually correct). A collaboration with the composer Michael Parsons exemplifies the intended sound quality best384. The problems with sudden bursts of noise and feedback described above, made it very difficult to employ this process effectively in practice. The process is either inaudible or vaguely noticeable, or within an instance ear-splitting noises can rapture through the proceedings. While limiting the audio signals allowed me to successfully 382 See Chapter 2 for definition.
383 Audio example Dazwischen, Defining Edges minutes 0:50 - 2:00.
384 Electronic version of Piano Piece 2002 by Michael Parson included on Data-DVD: file name:
tame these outbursts, the overall quality remained generally unsatisfactory during improvisations.
“Study III”385 and a solo performance at the UEA386 document an attempt to utilise this process by implementing a more algorithmic method that combines the tuning of the filter bands with visual feedback. Possible notes would be suggested on the laptop screen, enabling a more intentional relationship with the filtering process. The performer can choose to play or avoid the suggested notes or notes of the respective harmonic series. While a more generative approach would have allowed me to develop this strain of experimentation further, especially within a more compositional approach, a sophisticated filter bank (resonators~387) was eventually chosen to filter white-noise according to the analysed partials in the acoustic signal. In this way the loudness of the partials can be more easily controlled to avoid extreme dynamic ranges described above. In practice it has shown that this process works well in combination with the pitch module, as they are sonically related. Furthermore this process results in the elongation of partials, it has therefore an enhanced affect on the ‘horizontal axis’ of the spectrum. After the values of the partials were established through audio analysis, the process continues to work independently.