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cello solo v1

Cello solo v1

The cello solo will use my prepared cello: not a million miles from a prepared piano as mentioned in previous blog post. The preparations make pitch quite indeterminate, so rather than generate a stream of pitches (like for the guitar/piano) what I wanted to generate was essentially a tablature score for the cellist to create a stream of actions that would limit the indeterminate pitches in different ways to create loose patterns. Tablature notation differs from standard notation be being more about telling the player what do (what actions to carry out, where to put fingers etc.) rather than what sound/note to make. It can be especially useful in situations where the specific pitch result is indeterminate so instead the notation deals with timing, positions etc. See Aaron Cassidy's scores and writings on this as a good example. Below is a page of his solo for any bowed-string instrument, with staves for: (top) fingerings and bowing on the four strings; (middle) finger-width spacing on a scale of 1/tight to 5/wide; and (bottom) left-hand position on the fingerboard, written according to string conventions for playing scales (i.e. 1st position, 2nd position etc).

ex.1: The Crutch of Memory, tablature score for bowed-string instrument by Aaron Cassidy.

My cello preparations involve plastic or metal objects (currently a triangle-shaped wedge) placed between two strings: see ex.2 video below where I talk through the preparation use. These objects act partially like a finger on the string in something between a harmonic pressure and a fingered pressure. So the position on the string can be heard as a pitch (or pitch colour at least), but the harmonic-like pressure also means that the main timbre component is like a harmonic rather than a stopped note. Further complicating this, the preparation itself channels vibrations from one string to another, interfering with it, and the weight of the preparation alters the ration of string mass to length, which changes it's harmonic structure into an bell-like 'inharmonic' timbre. When this is bowed, the sound splits into different harmonics and multiphonics in a way that is specifically indeterminate but can be locally navigated.

ex.2: cello preparation example.

Initially I thought that Xenakis' 3D cubes would be the best way forward, because it's essentially a permutation system that would allow me to create a constantly changing pattern based on a number of elements. So I designed a basic cube (see ex.3-left) that used an inner set of durations (to create a rhythmic pattern) and an outer layer of dynamics; though it should be noted that the cello preparations make the string very sensitive, and using different bow force/speed can give very different pitches (harmonics), so really the dynamics here are just a shorthand for 'force', not necessarily loudness. Since different dynamics can give different pitches, I essentially now had a way to generate a stream of notes.

ex.3: initial 3D cube attempt (left) and isorhythm 1st attempt (right)

However, I became dissatisfied with the cube because the pattern I wanted had too few elements. 3D cube technique would work better with lots of different elements, so I tried an isorhythm instead. [Now that I write this blog I realise that I could have used more dynamic cube structures that would have allowed more rapid change by switching the few elements mid-line etc, maybe I'll try that later in the piece.]Isorhythms work well when the different parameters have prime numbered amounts, so they take longer to come back to the initial pattern and repeat themselves. My first attempt (see ex.3-right) was to use:
  • 7 durations, 5 forces (dynamics), and 3 positions
'Positions' here are the divisions of the space between the preparation and the bridge; since the preparation acts like a finger on the string. An even division of the string doesn't work here, since I've found by experimenting with the preparation that I can get three different sound-types: 
  • by bowing close to the bridge (sul ponticello) I get several very high harmonics. 
  • bowing right beside the preparation (sul tasto, which really means over the fingerboard, this is extreme tasto) gives a very quiet subharmonic rumble. 
  • and bowing anywhere else between those extremities gives a mid-range pitch or multiphonic depending on pressure.
ex.4: dividing the string according to different types of sound produced

This isorhythm was fine, better than the 3D cube because I now had less elements but permutating better. However I needed to make some elements happen less often, especially 'forces'. So I doubled or tripled the length of the isorhythm, which gave me more elements to play with, allowing some elements to only happen once in 14 times rather than once in 5; a much slower rate. My new isorhythm also had more parameters.


  • 14 durations, 10 forces, 9 bow touches, 11 motions (called 'movements' in ex. below)
This was a significant development in several ways. In ex.5 below you can see the effect especially on the forces, which have continuous stretches of quiet forces, with brief forte interruptions. The introduction of a 'bow-touches' parameter allows a nuancing of the forces with stretches of different bow pressures: including flautando, a light-fast bowing that brings out upper harmonics, and 'slow' bowing is the lowest bow-speed that still allows pitch to form, often introducing multiphonics and noise/scratch components. The isorhythm means that these touches cycle against the forces at a ratio of 9:10. also important to note that none of the forces and touches are contradictory: e.g the different bow parameters are always interacting, this reduction to two parameters is a simplification that still works, a forte flautando gives a different result to a quiet flautando, the bow is still fast but less light. 

Another new development was to first expand the positions from three to five, by expanding the 'mid' position from ex.4 to acknowledge there are more distinct sounds in there. However, the isorhythm meant that the player was simply moving along the five positions in different rhythms, too predictable (even taking into account the indeterminacy). So instead of having absolute positions (analogous to absolute pitches) I switched to making the 'position' isorhythm relative instead: see upper right-corner of ex.5. This results in isorhythm elements that can be 'steps' (moving to the next nearest position), 'leaps' (jumping to a further away position), staying in same position, and one special 'change preparation' where the preparation is moved to a different position on the string: a meta change that then alters the indeterminate pitches of all the positions. Additionally, the 'motions' line reverses on itself when the end is reached; rather than starting again as the others do: this means the 'change' element only appears every two cycles.





ex.5: isorhythm v.2

Finally, the bottom of this sketch shows some future thoughts and other larger structural considerations.
  • as with guitar/piano I'd like to add later another layer of disruption such as grace notes (two per cycle), and nail-pizz (once per cycle). Similar to this but on a higher structural level, once in the section there'll be a very long slow bow that steps outside the metrical rhythm of durations, taking 30–40 seconds to complete one single bow stroke so slowly that pitch can barely stabilise.
  • I may also add a scaling factor so that some cycles of the isorhythm will alter the base tempo, making the durations longer or shorter. This fixes the issue of the rhythms being too repetitive.
  • The choice of preparation positions on the string will be governed by the main underlying pitch at that place on the string; although that doesn't specify what other pitches will be available, it means there will many more 'E' pitches present in the cello solo, giving it a pitch anchor.

Key Commentary points

For my 1000wd commentary, the key points that I might include are:
  • this type of of preparation on the cello means the pitches are indeterminate, so I'm using a tablature-style notation rather than standard stave notation; which is pitch-centric (focusses on specific pitches). I'd explain the details of the preparation in an appendix with pictures and audio/video examples, using the commentary itself to explain how this affects compositional decisions.
  • the isorhythm changed a few times to ensure I had mostly subtle changes with occasional larger changes. And I developed changes that happen at a micro-level (note-to-note) but also macro-level changes that only happen a few times in the section and feel like 'paragraphs' rather than 'sentences'.

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About the project

I'm a composer and lecturer at the University of Leeds, UK. As part of our undergraduate composition teaching we introduce various flexible generative techniques, and an expectation that students write a commentary that outlines their compositional process. To give the students another example of how this can be done, I've decided to compose a piece [jump to final piece] for the student new-music ensemble that explores several of these techniques; to augment existing examples, and give a more first-person account of using them. This blog follows my process as I compose using some techniques that I've taught often but wouldn't normally used myself: see here for examples of what I do usually.

[Impatient? go straight to the finished score, or watch the video]

Here's what I begin with:
the ensemble is unusual to say the least, but I like a challenge!3 fl, 2 cl,  sax, tpt, cornet, euphonium, perc, piano, guitar, celloRehearsals begin in February 2018 with performance in…

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[general apologies for the images in this post, which don't always link easily to the text. My parameter names kept changing over the few days spent composing this, which looks confusing now because the parameter names (descriptors) aren't always the same.]
Having generated the phrases for the guitar and piano, I need to decide how this 5-mins of duet will relate to the rest of the ensemble. I decided to use the Xenakis rotating-cubes technique to generate a phrase-by phrase orchestration behaviour. Crucially, this only defines the type and size of orchestration, not the specifics: I could have generated very specific limitations on instruments etc but wanted to keep this free to save time really, and allow a more intuitive shaping of that aspect. I also wanted to avoid this being too 'blocky' and only mirroring the phrasing of the duet, so I allowed for some orchestrations to reach forward or backwards into neighbouring phrases. My first thoughts on this is that I ne…