Before I started to produce the sound material for this piece on the computer I designed a set of eight initial structures based on all-interval series ( series of pitches that do not only contain all twelve chromatic tones, but also the eleven intervals from minor second to major seventh). These structures were applied to recorded piano sounds. (No special techniques or preparations were used while making these recordings.)
Some of the recorded tones turned out being too short to fill the initial structures’ prescribed durations. In such cases the duration of a tone was extended by adding the same tone in reversed direction (the resulting symmetrical envelopes became a strong characteristic of the piece).
The initial structures were used in two ways:
1. as a sound source
2. as a filter (spectral envelope)
In the first case the interval structure of the series of piano tones was maintained, while another series of (electronic) sounds* was used as a spectral envelope to create a new timbral fluctuation. In the second case the interval structure of another series of sounds was enforced onto the piano tones, while the timbral flow of the piano tones was maintained.
In both cases, silences occur at moments where either the source structure or the filter structure has no information. The different parts of Apertures span a range from completely monophonic structures (“Monodie 1” and “Monodie 2”) through timbral chords (“Synchronisatie 1” and “Synchronisatie 2”) to a time-shifted synchronisation of form variants (“Canon”), and ending with a more or less serial construction (“Slotstructuur”).
In the winter of 2004, I started to work on corrections of Apertures; corrections that eventually developed into a continuation of the original piece. More Apertures starts with a reprise of “Monodie 1”, after which “Synchronisatie 1”, “Synchronisatie 2” and “Canon” are introduced in extended forms based on the addition of transpositions of their individual elements (chords). The longer silences in the extended “Canon” were now filled with unprocessed voice material from Stimmlich: the same material that served as input for cross-vocoding during the production of the material for the original version of Apertures. From there on, form sections based on transformations (made in Kyma) of these extended parts are presented in an overlapping form. When I played More Apertures to Richard Barrett, he immediately suggested to combine the two pieces into one piece of almost an hour. His comment was spot-on as always; the increased demandibillity of the piece as a whole makes it more challenging and therefore, contradictory as it might sound, more accessible at the same time.
Apertures – More Apertures is dedicated to Richard Barrett.
*sequences of electronically modified voice material from my compositions Paradigma and Stimmlich.
score example 1 
score example 2
year: 2000–2005
duration: 53:20
tracks: 8