Norwegian violinist Bjarte Eike’s Alehouse Sessions have become something of a classical shibboleth – an after-hours musical secret that has inspired a cult following and evangelical enthusiasm.

To see the group live is to be instantly converted to their eclectic, offbeat brand of Baroque-folk crossover: the free-flowing ‘sets’, the dancing, the bottles of beer, the playful banter with the audience. Their debut recording (9/17) was an all-out musical party, wild with dances, dalliances and drunken brawls. The follow-up is an altogether mellower and more polite affair but has lost none of the original’s joyful, idiosyncratic spirit.

Eike and his musicians swap the alehouse for the playhouse – almost. Taking inspiration from Cromwell’s England, when the closure of the theatre drove music-making underground, they imagine an evening in the tavern in which London’s out-of-work court musicians mingle with locals, creating a spontaneous recital of everything from Purcell to sea-shanties, jigs and folk songs, and even some spoken drama.

The natural affinities between Purcell’s circling ground basses and jazz riffs, between Baroque rasp and folk music’s undone, informal tone have been thoroughly explored by other groups. The success of these particular treatments – of episodes from The Fairy Queen, Dido and Aeneas and Come ye sons of art, as well as the inevitable ‘Music, for a while’ – is their ease. Rhythms might pulse a little more noticeably, pizz strings replace bowed ones, syncopation sometimes swells stronger, singers coax and croon as well as project cleanly, but there’s no effortful or pointed rewriting, just a gentle blurring of genre boundaries (plus some seriously stylish playing and singing from all concerned).

It helps that the ‘sets’ allow one work to dissolve imperceptibly into another, taking us from (for example) the Prelude to Act 5 of The Fairy Queen straight into the gentle groove of a Norwegian folk dance.

The repertoire – a selection of English and continental folk songs and dances, many arranged by Eike, interspersed with bits of Dowland and Purcell – treads similar ground to ‘The Alehouse Sessions’. But there are some interesting differences. An expanded group – up from nine to 11 performers – not only gives us more textural variety but also adds women (cellist Judith-Maria Blomsterberg and soprano Berit Norbaken, the latter’s delivery beautifully clean and unmannered). We also get newly composed works by Eike himself – Shakespeare settings, mostly – that blend unobtrusively into the prevailing style and help outline the broad A Midsummer Night’s Dream-shaped narrative.

It’s hard to put your finger on the ensemble’s distinctive appeal but it seems to be a sort of strange reverse alchemy. These are expert musicians who take off their professional hats and muck in as needed, playing multiple instruments and all singing both as chorus and soloists, creating a performance that may not be authentic in a strict historical sense but feels absolutely authentic to the spirit of the period and of players – as then, and as now.