Imaginary Numbers is experimental composer Betty Widerski’s foray into live looping using mainly violin and viola. To a point, the idea works well. The first three tracks find Widerski, aka Reverse Polish Notation, improvising over her loops, building her sound a phrase at a time. These, to me, are the strongest pieces here. “Rainforest” opens the disc with a slight Asian flair, a swirling arpeggio singing over a dialogue between plucked and bowed melodies. “Ashes”is my favorite piece on the disc, a work that patiently builds from an insistent string pulse and a knock-on-wood rhythm. Where “Rainforest” built its layers quickly, “Ashes” generates a feel like someone else has just walked in and pauses before adding to the movement. There’s a beautiful sadness here, a true ache of the soul in Widerski’s strings.  “Tango de la Luna” is rich and befittingly dramatic. The looping here comes off more as Widerski’s backup combo keeping time rather than a simple repeating backdrop. The appeal in these early tracks is the way they seamlessly blend the intimacy of a chamber music performance with minimalist undertones, paired with the knowledge that Widerski’s doing it alone. Unfortunately, the wheels start to come off for me with “Subterra.” The computer-generated beat feels out of place in the wake of Widerski spending her first tracks investing the listener in the idea of complex rhythmic structures being formed through loops. Granted, this track is (as noted on the cover) an improvisation over computer-generated noises, but the unchanging beat becomes monotonous, and it pulled me away from the more interesting aspects of the piece. She follows with a straightforward version of a traditional tango, “Tango a Unos Ojos,” which she arranged and on which she also plays piano. It’s a temporary, quite lovely, respite before the final two tracks. I have listened to them, but as they are straightforward songs, I would prefer simply to say that I don’t review songs and leave it at that.

The strength of this disc, while it lasts, is Widerski’s playing. The tones are rich and warm. Strings always have such a human sound, even if it’s often mournful or crying. Here they are, in fact, cries, but they’re also laments, shouts of joy, and stories, pushing against the formal and unwavering rigors of the looped structures. Imaginary Numbers misses more than it hits for me, but when it does hit, the impact is memorable.

Available from Reverse Polish Notation’s web site.