The orthogonal axes chosen for the transverse waves is chosen because of the asymmetric coupling in the two directions. On a flat-top acoustic guitar the top plate moves up and down "more easily" then from side to side.
Fragment of CONTRACTIONS, mobile for woodwind quintet 1965. Each of the 5 players follows a concentric circle in either direction. Graphic notation alternates with traditional notation. Originally published by E.C. Schirmer, Boston. Copyright transfered to Richard Felciano in 2003. By permission.
1970-1980: The period Felciano conducted the San Francisco Symphony in performances of Galactic Rounds, whose rotating trumpets and trombones created Doppler shifts in the San Francisco Opera House. Behind him is the travel version of the Buchla 200 Series analog synthesizer, which he used in his 14-channel environment with light sculptures for Boston's then-new City Hall.
