Maverick composer and cornetist Rob Mazurek formed the Exploding Star Orchestra in Chicago in 2005, drawing on some of the city’s most exciting young jazz players. Mazurek is known for straddling the line separating modern improvised jazz and post-rock; he has released several records on the Thrill Jockey label and was joined on his 2009 record Sound Is by members of Tortoise. On paper, the present ensemble of 14 pieces seems a bit on the small side for an orchestra, but they make a big sound, thanks largely to Mazurek’s liberal application of electronics and pre-recorded sound.

Stars Have Shapes is an unusual conception. The bulk of the record is occupied by two dense, 20-minute constructions, less songs than sound environments within which the musicians converse and explore. Following each is a comparatively brief composition in a more straight-ahead melodic style. The format gives one a welcome breather in between the longer and more intense tracks.

The album opener, “Ascension Ghost impression #2,” is essentially an extended diminuendo, beginning with deafening sheets of electronic sound through which the musicians fight to be heard and finally settling into a quiet equilibrium some 20 minutes later. The second, much mellower long number, “Three Blocks of Light” places the Orchestra against a shifting backdrop of electronic drones. Some of the sound sources are more distinctive on paper than in practice (“insects at the turn of an eclipse,” “Drones built from electric eels”) but the record remains compelling throughout.