Lovers of jazz will need no introduction to Herbie Hancock.

Maverick pianist from the days of the Miles Davis quintet, preferred keyboardist of the Davis fusion years and central energy of the seminal funk-jazz crossover album Head Hunters. Herbie Hancock has never been afraid to experiment with forms and genres, to explore the possibilities inherent in different music.

However fans of Joni Mitchell may not be so well acquainted with his work. Though Joni has never been an artist to shy away from incorporating elements of jazz into her folk and rock idiom she has never quite made the step from those idioms to jazz. All of which makes the new Herbie Hancock recording, River: The Joni Letters an intriguing listen.

For this album Herbie Hancock has assembled an eclectic mix of musicians. Saxophonist Wayne Shorter, his fellow traveller from the fusion years, bassist Dave Holland, drummer Vinnie Colaiuta, and west-African guitarist Lionel Loueke. There are also appearances by a number of leading luminaries, Tina Turner, Corinne Bailey Rae, Luciana Souza, Norah Jones and Leonard Cohen. Mitchell herself guests on a track.

Projects like this can go astray, fall between the contrasting drives of their respective genres. Yet it is to Hancock’s credit that this album delivers. It manages an adroit balance between accessibly and improvisation without sacrificing musical integrity. It plays with Hancock’s jazzier instincts and the limitations of the rock and folk idiom. It elaborates on the subtlety of Joni Mitchell’s melodies and provides a sophisticated setting for her often quite excellent lyrics. It manages to be neither a Joni Mitchell album nor a Herbie Hancock album. Instead it occupies a space somewhere between the two.

That is not to say it is without flaws. The title track, "The River," comes over a little too sweet. Corrine Bailey Rae’s vocals sound to my ears somewhat girlish, smothering the ironical longing of the lyrics; Also, Norah Jones’s vocals on the opening track, Court and the Spark, appear at times to get lost, to sink below the music. And the final track, one of two bonus tracks, A Case of You, while infectious and cross referencing Afro-Pop, folk and R&B could be considered superfluous.