Hans Tammen calls his style of performance "endangered guitar," presumably because of the extreme alterations he enacts upon his instrument's sound and construction. Tammen "prepares" his guitar in much the same sense that John Cage prepared the piano; he also processes and manipulates his live sound through a computer system that's based on Cycling 74's Max/MSP program. Tammen was given his first guitar by his grandfather at age 15 -- an old instrument that had been lying in a basement. Influenced by rock groups like Uriah Heep and Deep Purple (the latter's guitarist, Ritchie...