From the beginnings of free improvisation in the 1960s, proponents subjected their instruments to unprecedented interrogation, in pursuit of the instrumental impulse.  This is shown in the work of Swiss-German trio Kimmig–Studer–Zimmerlin: Harald Kimmig (violin), Daniel Studer (bass) and Alfred Zimmerlin (cello). On this recording, the instrumental impulse is exuberantly expressed, in what Studer prefers to call “improvisation without any prefixed compositional tool".  The trio pull, grab and smack their strings, scratching and striking the body of the instrument, using it as a resonator. These are not mere "extended techniques". – Andy Hamilton