Despite herself, Nadia Boulanger (1887-1979) is increasingly established as a composer. She was known to describe her youthful pieces as ‘useless’, having moved on to teaching great composers from Aaron Copland to Philip Glass and promoting the music of her brilliant sister Lili Boulanger (1893-1918), who died as she was reaching her full maturity. Here, the sisters are paired over three discs, Nadia with 38 mélodies written between 1901 and 1920, and Lili with 17 written between 1904 and her death, including the great song-cycle Clairières dans le ciel. Sprinkled throughout are songlike instrumental chamber works by both composers.

Lili has long been known as one of French music’s great might-have-beens, and her mélodies have been attractively recorded elsewhere. Nadia’s little-known works have been turning up mixed in with those of her sister, though this set was right to put the two composers on separate discs, and for Nadia to go first. Their artistic kinship is apparent, not just in using the same poets (Verlaine, Maeterlinck, though Lili cast a wider net to include Heine) but in employing similar compositional building blocks. Strophic songs were more for music halls. These art songs are mainly through-composed, and often with ostinatos and otherwise repeating motifs in various shapes and forms, used to keep the poem and the rhapsodic vocal line aloft.

Once Nadia found her voice, she was like a feet-on-the-ground Debussy with more stable, traditional foundations, or like Fauré with caffeine (she was mostly under 30 in this period). Like Schumann, Nadia’s artistic values are illuminated by how she massaged her texts, often leaving out numerous stanzas and replacing the poet’s words with her own – annotated in detail in the booklet by Anne de Fornel. As Nadia famously said, she thought in notes before she thought in words. Vocal lines freely do away with stanza divisions at times.

With her choice of texts (in one case she wrote her own), the Nadia mélodies reflect the backdrop of her times – of Pelléas et Mélisande (1902), the First World War, the death of her sister, but also the 1914 death of her mentor, lover and compositional collaborator, the celebrated pianist Raoul Pugno. Tangible evidence of what she lost is heard in her Pugno collaboration, the quite enjoyable cycle Les heures claires, which has simpler foundations and a cleaner sweep in the vocal lines. On her own, Nadia could be distinctively rhetorical: she could all but halt a song’s pace for a near-operatic pronouncement, such as the stoic portrait of a young mother waiting for her husband to come home from the front in ‘Soir d’hiver’. Her final songs from 1920 (the year before she gave up composition completely) include the stark, dense, dissonant ‘J’ai frappé’, a harsh encapsulation of aloneness.

After two stimulating discs of Nadia, one turns to the Lili disc to find a compositional vision on a higher level. If Nadia was comparing herself to her sister, it’s no wonder she gave up. The compositional building blocks do double and triple duty, providing both structural and harmonic support plus word-painting. The 35-minute cycle Clairières dans le ciel, with poems by Francis Jammes, ends with the remarkable six-minute ‘Demain fera un an’ that seems inspired by the final ‘Der Abschied’ from Mahler’s Das Lied von der Erde, and does not suffer in comparison because it has such a strong identity of its own.

But with the precedent of authoritative recordings of Clairières dans le ciel by singers such as Jean-Paul Fouchécourt and Nicholas Phan, one is left puzzled by Raquel Camarinha’s scrupulously demure, at times colourless (and even vibrato-less) approach here. An Urtext performance? In other songs, the vocal line-up is less than ideal. Stéphane Degout still has the soul and sensitivity of a song recitalist but a voice that’s now scaled more for the broader strokes of opera.

The main vocalist on the set is Lucile Richardot, and though all of her recordings have been major events up until now, this one has her a bit out of her element. Though her sung French is some of the best out there, the voice doesn’t bloom in places warranted by the songs but instead reveals a steely vocal core. Nonetheless, pianist de Fornel and her contributions to the booklet make the whole package an insightful, historically significant tour of two of 20th-century France’s great musical minds.