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Piano and Guitar duet v.2 - realisation

It's been two months between deciding the system I'd use for this duet, and actually implementing it. Inevitably a few things have shifted, but it's essentially the same as described in the first post here.

Part of the delay was laziness about transferring the stream of numbers into notes on Sibelius, which it turns out was solved easily by using the 'seq' object in Max to turn the stream of numbers into a midi file, which could then be opened in Sibelius. Easy!

The other delay was in trying to work out how the notation would work to (a) allow the guitar and piano to be together but drift apart at times, and (b) still allow the ensemble to play over the duet without requiring the players follow the conductor too strictly. The delay was one of those situations where I decided to just let me brain work on it without me (mulling it over sometimes without actually thinking about it too hard), and then some helpful chats with other composers made it fall into place.

I also had to figure out how to generate the drifts between the two instruments. In the end I took the generated stream of numbers and colour coded it to easily show the head motif—pitches 5, 9, 15, 19, 23, which equals E, G#, D, F#, A#: in Ex.1 the head proceeds from darker to lighter shades of orange, non-motif pitches are white—then anywhere there was a partial version of the head I would double it with a complete version. The pink section in ex.1 shows a very incomplete motif in the upper line against a complete one in the lower line. In the score, these two would either literally overlap (one instrument plays the complete version while the other plays the drifted version) or hybridise the lines by working some of the drifted notes into the complete motif.

In hindsight, I could have then started overlapping incomplete (already drifted) versions of the motif against even more drifted versions to take this further, maybe I'll do that later...

Ex.1: overlapping the head motif to create drifts.

In the actual realisation, I take more intuitive approach, taking the longer drift sections and sometimes lining them up against more complete motifs, but sometimes distributing the notes differently, transferring some from one instrument into the other. See ex.2, and more significant drifting shown in ex.3.
Ex.2: showing transformation from generated stream of notes (bottom stave) to guitar/piano.

Ex.3 more significant drifts from the original motif.
Guitarists maybe scratching their heads at the harmonics, but the guitar is in a scordatura tuning (E, G#, D, F#, A#, E) to allow the head motif to be played as 12th-fret harmonics.

Commentary notes:

While the system generated the sequence of notes (from a carefully tweaked algorithm), there is a lot of intuition in how this section unfolds. Many of the drifting sequences are distributed between guitar and piano in a highly unsystematic way, focussing on particular harmonies or timbres etc, but always in direct response to what I'm presented with. at that moment.


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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]

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piano & guitar 3 - orchestration

[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…