PTOLEMY HELICONA (VERSION 1: 8 August 2022)

   DESCRIPTION
   Ptolemy's Helicona can be played via keyboard and mouse:
   Press keys '1', '2', ... '6' to tune the instrument to various Greek scales (default: '4').
   Press keys 'a', 's', 'd', 'f' to play the lower tetrachord in the selected tuning (LEFT HAND).
   Press keys 'u', 'i', 'o', 'p' to play the upper tetrachord in the selected tuning (RIGHT HAND).
   Press keys 'v', 'b', 'n', 'm' to transpose all pitches up by 0, 1, 2, 3 octaves (from default 'v' = 0).
   The moveable bridge can be turned through the mouse:
   - click: activates the handle
   - turn the handle by mouving the mouse
   - click again: sets new position