{ Polyhonic variables are, in constrast to all other variable types, not global
  variables, but instead they exist separately in each event. Which circumvents
  the problem that (global) variables may be altered undesiredly if event
  handlers are called in "parallel". Downside: polyphonic variables need to be
  allocated as many times as events exist in the system. Thus: one single
  polyphonic variable takes a lot of memory! Due to this reason, only integer
  variables are allowed to be declared as polyphonics ATM. }

on init
  declare polyphonic $p
end on 

on note
  message($p)
  $p := $p + 1
  message($p)
  $p := $p + 1
  message($p)
end on