One of the highlights in the discography of this trombonist/composer/improviseror just use the term he prefers, sound gathereris the one he made in 1989 with Pauline Oliveros and Panaiotis in an underground cistern at Fort Worden. The two-million-gallon concrete tank has a reverb time of 45 seconds, almost certainly the longest of any acoustic space in the world; it turns every sound into a long tone, and the echoes of his trombone and of his colleagues' voice and accordion bounce off every surface and layer and circle each other, almost as if the sounds have become three-dimensional objects, creating sonic effects more wondrous than any electronic processing could do. As Dempster puts it, it is impossible to tell where the performer stops and the reverberation takes over. . . it slowly move[s] from the sound source along the walls until it envelop[s] the listener. Which forces one, more than any other setting for improvisation, to choose ones notes carefully, since no sound lasts less than 45 seconds; always deeply attuned to how his sounds interact with everyone elses, Dempster is perhaps the ideal musician for this space. Tonight, he and Brian Pertl (playing didjeridu and conch shell) will revisit the cistern for a special performance. You cant go down there with them, but their music will be broadcast to those on the lawn above.