Composed in 1998 for the newly fledged Ensemble Modern Orchestra, Heiner Goebbels' Walden, his 70-minute piece inspired by Henry David Thoreau's early classic on environmentalism, was imagined as a counterpart to Goebbels' suite Surrogate Cities, using similar images in a rural rather than urban context. Ten years later the piece was reworked for the Dutch-based Ensemble Klang, and in that stripped-down version it has received a new lease of life. Klang brought their Walden to Birmingham for the work's UK premiere, presented in collaboration with Birmingham Contemporary Music Group, which supplied the string players.

Goebbels describes his pieces as "a few musical sketches", leaving it to the instrumentalists to elaborate their roles further. The Klang version is built around the composer and improviser Keir Neuringer, who not only reads the extracts from Thoreau's writings, but also contributes saxophone solos, percussive sound effects and ambient scrapes and rustlings to the soundscapes with which they are surrounded.

There are some wonderful textures: an ever-changing mix of the notated and the improvised that pulls in generic ideas from the rock music of the last 40 years and involves a whole range of sampled sounds and exotic and newly developed instruments. But the overall effect is strangely abstract, and the connection between the sounds and the texts that supposedly inspired them is hard to follow, though it might have helped had the printed programme included the titles of the nine movements into which the work is divided. Listing the names of the instrumentalists involved would have been courteous, too.

Goebbels' works are notoriously hard to categorise, but Walden seems harder than most. There is too little context for what we hear; the allusive layers of text, music and image that are such a feature of his output seem far less rich than usual. You might appreciate what's going on but never really connect with it or feel transported by it.