On the surface, there is little connection between cherished Brit icon Robert Wyatt and cherished icon-in-the-making Antony Hegarty beyond the fact The Unthanks covered a selection of both over two nights at London’s Union Chapel in December 2010. But both singer-songwriters are unified by being highly idiosyncratic and intuitively melodic mavericks with a stark, intimate simplicity that often unfolds as luminous ballads. As Unthanks pianist and producer Adrian McNally says of both, "There is never a spare note played or one struck to impress." On top, both songwriters have a very strong political polemic that doesn’t overwhelm with sloganeering. How fortunate that The Unthanks come from the same tradition, while Rachel and Becky Unthanks’ voices are blessed with that same stark, intimate simplicity. In other words, it’s a perfect match.

The covers come in two halves. First, it’s six of Hegarty’s songs, mostly drawn from his breakthrough album I Am a Bird Now. Given Hegarty’s transgender politics and drive to establish a liberated perspective beyond machismo, it’s fascinating to hear his songs sung by women. Bird Girl is arguably Hegarty’s most heartbreaking tune, but For Today I am a Boy and You Are My Sister are more gripping because of their context. As older sis Rachel recalls between songs, she and Becky have a brother in-between their ages, and that Becky reckoned when she reached her brother’s age, she’d actually become a boy. Even better is hearing You Are My Sister sung to each other by sisters in blood as well as spirit, the arrangement and tone touching rather than cloying.

The nine Wyatt covers (well, eight, given Stay Tuned is written by Anja Garbarek but covered by Wyatt on Comicopera) are broader in spirit and intent, giving the Unthanks band more instrumental scope and even a playful interlude, namely the speedy clog-dancing that accompanies Dondestan. But they know that the ballads – which also match Hegarty’s primary soundscape – are the key to their connection with Wyatt. It’s hard to single out any of the eight beauties here but Lullaby for Hanza, Lisp Service, Free Will and Testament and Sea Song (also covered on The Bairns) are especially knee-weakening.

This album is the first in what will be a series of Unthanks albums titled Diversions, between official studio sets, as the band continues to look beyond the safe confines of whatever ‘trad folk’ is expected from them. Whatever follows will have a lot to live up to.