How do you fill a concert hall? This question is asked despairingly of venues across the globe, usually in one those gloomy articles which heralds the death of classical music with barely restrained glee. The Wigmore Hall does not seem to suffer from empty-seat syndrome, however Director John Gilhooly has struck on a smart solution to ensure that this malaise never strikes: diversification. Gilhooly approached one of the world’s most popular and respected jazz pianists, Brad Mehldau, and invited him to ‘curate’ a series of concerts, half of which would feature the maestro himself. Yesterday evening Mehldau was joined by Chris Thile, the man who plucked the mandolin from its twangy bluegrass origins and turned it into a virtuoso instrument at the cutting edge of jazz performance.

Thile first appeared onstage alone to perform The Louvin Brothers’ hit Broad Minded in his inimically extrovert style, alternating displays of technical brilliance with simple accompaniment to his expressive vocals. As a demonstration of his versatility, this was followed by the three inner movements of Bach’s D Minor Partita for solo violin. Both Thile and his mandolin may have sprung from bluegrass beginnings; however they have both achieved the level of accomplishment where any musical style is ripe for the plucking, if you’ll pardon the pun. Thile’s Bach was confident and musical, the mandolin sounding curiously appropriate, like a harpsichord with the added advantage of a greater range of dynamics and colour.

Thile was then joined by Mehldau for what was their first public performance together, beginning with When it Rains, taken from Mehldau’s solo album Largo. It was clear that both artists were tentatively getting to know each other as they performed, each shyly suggesting harmonic developments taken up with enthusiasm by the other. The pairing was instantly successful: Mehldau’s balmy piano sound and deeply intellectual approach to structure, complement Thile’s zanier, more exuberant style perfectly.

The evening was divided by the very different personalities of the two: Mehldau’s thoughtful, exploratory sets were interspersed with some of Thile’s own songs, including the morally dubious yet terribly funny Alex, in which the singer persuades the eponymous heroine to leave her boyfriend at home and paint the town red with him. Thile’s voice soared in the hall’s generous acoustic with a warmth not evident in his recorded works, whilst Mehldau used his sustained sound to great effect as an engaging springboard for Thile’s vocal and instrumental acrobatics.

The tentativeness of the first set melted quickly away as the pair hit their stride, the relationship seeming to grow more comfortable with every harmonic shift and glancing agreement. It was startling to see the rate at which the two soloists became a duo, a demonstration of the flexibility of these two great artists and a lesson in the art of ensemble.