Before I started to produce the sound material for this piece on the computer, I designed a set of 8 initial structures that are based on so-called 'all-interval rows' (a row of pitches that doesn't only contain all 12 notes, but also the 11 intervals from minor second to major seventh). These structures were filled in with piano tones that were recorded on tape separately. No special techniques or preparations were used.

At some points the recorded tones turned out to short to fill the prescribed duration. In these cases the duration of the tone was extended by adding the same tone in reversed direction (the resulting symmetrical envelopes would become a strong characteristic of the piece). These initial structures could be 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 is maintained, while another series of (electronic) sounds* is used as a spectral envelope to create a new timbral fluctuation.In the second case, the interval structure of another series of sounds is enforced on the piano tones, while the timbral flow of the piano tones is maintained.

*for this I have used sequences of electronically modified voice material from my compositions "Paradigma" and "Stimmlich".

In both cases silences occur at those moments where either the source structure or the filter structure has no information.The different parts of "Apertures" span a range from completely monophonic (Monodie 1 and 2) through timbral chords (Synchronisatie 1 and 2) to a 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", which soon 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" are now filled in with the unprocessed voice material from "Stimmlich", which is 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 (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 one hour. As always, his comment was spot-on; 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 for obvious reasons!