The billing promises much, and the performances certainly deliver. Colleagues in Baroque oratorio and opera for nigh on a decade, Carolyn Sampson and Iestyn Davies make a symbiotic partnership in these assorted duets, their tone (not least their control of vibrato) and style ideally matched. They are compelling interpreters, too, with an infectious sense of shared enjoyment in the Purcell-Britten ‘Sound the trumpet’ (Sampson’s whooping, unscripted octave leap guaranteed to provoke a smile) and the fumbling adolescent eroticism of ‘Celemene’. Here and elsewhere Joseph Middleton fully savours the ingenuity and extravagance of Britten’s piano realisations. Amid the duets, Sampson sings ‘If music be the food of love’ with an easy fluidity and grace. Davies floats an ethereal line at the opening of ‘Music for a while’ (shades here of Alfred Deller), then vividly dramatises the dark central section evoking Alecto’s serpents and whip. This favourite song is not merely soothing, all the more so in Britten’s arrangement.

Mendelssohn and Schumann would doubtless have raised an eyebrow at the notion of a falsettist – a breed all but unknown in 19th-century Germany – in the Biedermeier salon. Countertenors who have ventured into Lieder are apt to sound flustered or petulant when they strive for passion. Iestyn Davies avoids this trap, choosing slow, reflective solos that display his otherworldly purity of tone and serene legato. Mendelssohn’s elegiac barcarolle ‘Scheidend’ and Schumann’s quietly majestic ‘Nachtlied’ – more chromatically troubled than Schubert’s setting of Goethe’s famous valedictory poem – are highlights, as is Carolyn Sampson’s fleet, smiling ‘Aufträge’, abetted by Middleton’s diaphanous accompaniment. The duets – superior salon music – are all enchanting. With Middleton always an animated partner, the singers blend mellifluously in all those caressing thirds and sixths, with refined phrasing and an unselfconscious charm, not least in the shimmering excitement of Mendelssohn’s ‘Maiglöckchen’, in his fairy scherzo vein, and Schumann’s blithe quasi-folk song ‘Schön Blümlein’.

Euphonious charm is the default mode in the solos and duets by Roger Quilter, whose pleasures, like those of his French contemporary Reynaldo Hahn, are modest but durable. Even after several hearings I’m not quite convinced by the pairing of soprano and countertenor (rather than tenor) in the waltz duet from Quilter’s operetta Julia. But the other duets and solos, again, are a delight: in the calm intensity Davies brings to ‘Music, when soft voices die’, Sampson’s touching simplicity in ‘Drink to me only with thine eyes’, and her exuberance and ardour in ‘Love’s Philosophy’, with the voice soaring gloriously to the song’s climax.

Quibbles? Well, Schumann’s homely duet ‘So wahr die Sonne scheinet’ is too reverential for my taste. And both singers could have sometimes given their German consonants more bite without compromising the line. But this is nitpicking. Here is a captivating, unhackneyed programme, presented by singers – a double act in a thousand – and pianist with a style and allure it would be hard to beat. No one remotely drawn to this repertoire should hold back.