American-born, Berlin-based Catherine Lamb is a composer of microtonal music (or spectralist, depending on your point of view). In 2020 she deservedly won the Ernst von Siemens Composers’ Prize. This double-disc release, commissioned through the award, features two string quartets, each based on long – very long – sustained tones. The Jack Quartet, specialists in this idiom, play with precision and deep feeling, and the dry recording quality is microtones optimal.

string quartet (two blooms) is 45 minutes long and dedicated to Lamb’s teacher, James Tenney. After two minutes of one sustained violin note (no vibrato, no adornment, just catgut and string), a second violin enters – playing the same pitch. Discarding traditional features, Lamb establishes a different set of values, a slower sense of time. Psychoacoustic activity is to the fore: the beating that arises from two pitches ever so slightly deviating from one another; the additional tones that halo two non-identical pitches. Eight minutes in, we finally get more than just deviations around one note: two pitch centres, orbital to the first.

It is strikingly austere, and there is enjoyable strangeness in cleansing the doors of perception and hearing sound as it truly is. One quibble is the dearth of rhythmic interest. As with other composers in this lineage, Lamb, when talking about frequency ratios, can strike a utopian register. Tristan Murail once said, tellingly, ‘Music is harmony’; but it isn’t. Sometimes I feel that psychoacoustic system-building can come at the expense of recognising the broader domain of musical sound that isn’t so easily systematised.

The hour and a half-long divisio spiralis contrasts with the previous quartet. Although also based on sustained tones, it has rhythmic counterpoint and a more emotional quality, because of how the rhythmic activity, perhaps unwittingly, aligns the tones with the human voice. Beginning in a high register, the plangent quartet descends after one hour to a low register. Eventually, it ends beautifully with the cello playing a quasi-melodic line akin to Glass, backed by wild, shimmering microtonal frequency fields.