For the entire piece, the piano leads, and the other instruments (cello, clarinet and 'minimal electronics') compliment with restraint.  At first, there are mostly plaintive fragments of melody separated by silence...  They are whimsical; at first it's not clear whether this is composition or improvisation, and rightfully so: the liner notes reveal that this piece was created by electronically arranging fragments of improvisation, allowing for a perfect fusion of the two approaches.

As time goes on, there's more harmony and chordal interplay between instruments.  The clarinet begins to repeatedly sound a long tone each downbeat, later to be joined by the gorgeous sounding cello, which provides the most beautiful moments of the piece.  The loose 'progression' builds until an almost-coherent musical phrase asserts itself, and at that moment Phillips dissipates the piece into silence again.  This sort of movement happens many times.

To Phillips' credit, at no point does he fall back on any kind of traditional musical device.  He only hints at structure; each musical idea drifts off before ever forming into any kind of tonal pattern.  Yet the piece is clearly lovely, thoughtful, and full of feeling.  This sort of balance must be hard to strike.

The 'minimal electronics' Tomas uses are indeed quite sparse.  The only electronic elements I have noticed are piercing high frequency pitches sounding at very low volumes, making themselves known nonetheless due to their acute sharpness.  When they fade away, the surrounding silence feels all the more complete.

The opening phrase is the only element I've noticed repeating at different points in the piece.  A few minutes from the end, the beginning is reprised, and it ties things together nicely.  The piece feels like more than a directionless drift.  The actual ending is a new repeating chord with a contemplative, heady sound to it, again on the downbeat of each bar.  It fades out and it seems the piece was just long enough.

Tomas Phillips' "Quartet for Instruments" is a great album for anyone who can stomach atonal classical minimalism.  It's beautiful, challenging and reasonably unique.  I'm not always in the mood for a piece like this, but when I am it puts me in a very zen state of mind, and serves as a canvas for pleasant thoughts.