This is the first U.S. appearance (2008) of this 2003 disc in the DG 20/21 series. It has been available via Amazon.co.uk for years. Better late than never if it's your first chance to hear it!
"Theseus Game" is a fantastic recent work (33'14" -- 2002), a concerto for orchestra, with the thread of melody passed from one soloist to the next, winding through a complex, dynamic orchestral score. This is a live recording of the work's premiere performance in September 2003. The Ensemble Modern is broken into two groups (a la Stockhausen's "Gruppen") with opposing tempos (a la Elliott Carter) and conducted by both Martyn Brabbins and Pierre-Andre Valade. The recorded version lacks the spatial dimension of a live performance, as the players are dispersed, and move about, layering the sounds.
The new live recording of "Earth Dances" (33'22" -- 1985/6) from October, 2001 in Frankfurt, is great, a big improvement over the quite fine earlier recording by the Cleveland Orchestra, conducted by Dohnanyi (see my review). This new performance was conducted by none other than Pierre Boulez, and performed by an expanded Ensemble Modern. It is tighter, more dynamic, more visceral, and more powerful than ever before.
If you could only hear one disc by Birtwistle, this is the one!
(verified purchase from Amazon.co.uk)