Catherine Lamb works at the boundary between perception and illusion. In Curva Triangulus (2018/21), the American composer takes Bridget Riley's geometric forms as starting point for "warping" Renaissance materials through geometric musical figures. The result is a 41-minute composition for eight instruments where the distinction between melody and harmony dissolves: one generates the other, rather than existing as separate entities.

The score demands an exceptional ensemble. Bern's Ensemble Proton has access to extremely rare instruments: the arciorgano (Vicentino's 16th-century microtonal organ), a baroque triple harp (Barberini model), lupophone, contraforte, and clarinet d'amore. These combine with flute, cor anglais, bassoon, violin, and cello in an asymmetrical octet. The absence of piano and presence of the bellows-driven arciorgano subverts the ensemble's traditional balance, with the organ supporting the entire score from below.

Lamb imagined a late Renaissance position of musical perception, warped by Riley's triangles and shapes in multidimensional space. Italian composer Zarlino hovers as phantom presence (with echoes of Marc Sabat's Gioseffo Zarlino surfacing), while Rameau's intuition about the sounding body remains just beyond the historical horizon. The baroque triple harp acts as "free flowing agent," articulating the progression of clearer contrapuntal triadic material in the foreground.

Ensemble musicians alternate roles as active generators and passive harmonizers, always in relation to one another. In the revised version (completed winter 2020/21), these roles are distributed more evenly, adding timbral and intentional diversity. Richard Haynes introduces clarinet d'amore, while Elise Jacoberger contrasts bassoon and contraforte more distinctly. The ensemble includes Bettina Berger (flute, alto flute), Martin Bliggenstorfer (cor anglais, lupophone), Vera Schnider (triple harp), Coco Schwarz (arciorgano), Maximilian Haft (violin), and Jan-Filip Ťupa (cello).

Recorded at Guebwiller Cathedral, France in May 2023 by sound engineer Ingo Schmidt-Lucas, Curva Triangulus is the latest in Lamb's extensive Another Timbre catalog, following parallaxis forma, Prisma Interius VIII, string quartets with JACK Quartet, and earlier works. Dusted Magazine notes the composition possesses "undeniable and immediate beauty" with "leisurely pace allowing room for experiments," offering both deep listening challenges and accessible pleasure.