THIS year's International Festival is festooned with period instrument ensembles, what with the Orchestre des Champs-Elysées and Les Arts Florissants both in town last night, the English Consort at the Usher Hall next week and the excellent ongoing early music series at Greyfriars.

The Ricercar Consort, founded in Belgium in 1980, is among the most venerable of the lot.

It has a particularly genteel kind of appeal, soft in volume, timbre and expression and not as boisterous as many of today's early music outfits. Inevitably some of its subtlest touches got lost in the wash of Greyfriars' acoustic, but regardless: this was a beautifully soothing hour of music.

The programme was a celebration of Henry Purcell, starting off with a selection of his instrumental and vocal works and ending with an ode written after his early death (at the age of just 36) by his former teacher John Blow.

The Ricercars were joined by two countertenors – Robin Blaze and Carlos Mena – who alternated solos and duets. Both are interesting voices but weren't evenly matched: Mena's is the more florid and louder of the two, while Blaze often seemed stuck in an awkwardly low register that didn't really project.

Still, his heart-rending tugs and sighs in the recitative of Blow's Ode was some of the finest singing of the evening.

But in general it was when the Consort played alone that their artistry carried best – nowhere more than in Purcell's Chaconne in G Minor. This irresistible lament repeats its falling bass line no fewer than 44 times (so the programme notes told us) beneath a gorgeous tangle of keening recorders. Mesmerising.