Nicholas Phan recently opened a Philadelphia Chamber Music Society recital with a Nadia Boulanger-authored song I never knew existed, ‘Soir d’hiver’, with an effect so powerful that I feared I would never again hear this seemingly forgotten miniature epic about a woman waiting for her husband to come home from the First World War. Luckily, that song ends Phan’s new recital disc of songs by Lili and Nadia Boulanger, and is one only among many riches.

The music world is long acquainted with Lili Boulanger, whose death from tuberculosis in 1918 at the age of 24 is one of the century’s great musical tragedies. But her older sister Nadia (1887-1979) was also a notable composer before becoming the legendary teacher of composers ranging from Aaron Copland to Philip Glass. Juxtaposing the sisters highlights their individual musical identities. The musical godfather here is Debussy, specifically his 1893 Proses lyriques, with self-authored texts that allowed the composer to musically roam free, even more than usual. Both Boulangers are represented here by through-composed pieces whose starting points give not the slightest hint of a musical or poetic destination. Like Debussy, they often employ simple, sequential ideas in the piano while allowing the vocal lines to go where the words lead them.

Nadia builds her songs out of discrete modules with well-considered cumulative effects. Lili is more airborne and seamless, with unpredictable weather fronts of emotion that evolve out of and into one another, enabled by a larger palette of harmonic resources. However glistening the music’s surfaces, the disc is not an easy listen, with its poetic abstraction and free-ranging music.

In fact, one wonders if the main piece on the disc, the 13-song cycle Clairières dans le ciel (1914), owes its lack of visibility partly to its challenges – and the lack of any clear path to the manner in which it should be performed. The Francis Jammes text is written from a male viewpoint, looking back on a passionate but no-longer-existent relationship with imagery ranging from floral to religious (both customary at that time). Most memories are wistful, though with a few gothic turns, and with an ambitious final song, ‘Demain fera un an’, which Phan (in his excellent booklet notes) describes as reprising previous musical motifs much in the fashion of Faure’s La bonne chanson.

Phan’s primary precedent is Jean-Paul Fouchécourt’s 2007 recording on Timpani, with an articulate but less robust vocal production that navigates the upper registers with particular ease. But is ease what is needed here? Phan’s more mainstream tenor voice (he occasionally resembles Peter Pears) uses the upper range to reveal great dramatic tension in the music, with an intensity that can be downright operatic. Pianist Myra Huang matches him all the way, with especially fine effect in ‘Parfois, je suis triste’ where an out-of-left-field keyboard flourish conveys the protagonist’s quickly shifting memories.

Phan has deeply internalised this music – with highly detailed, personal, specific and often quite volatile responses to Lili Boulanger’s particular fusion of music and poetry in Clairières dans le ciel – though not through the lens of Debussy. Boulanger taken on her own terms. This less genteel approach to French art song has also been explored by François Le Roux; still, Phan is likely to be controversial. But to these American ears, Phan delivers a more emotionally comprehensive (and deeply welcome) vision of this worthy music.