o make current model survive restarts (e.g. turn screen).
o move creating thread inside the PitchFollowGame class.
o Note needs to be serializable to survive state change
  (does not seem to work yet while playing game ... need to investigate).
o Have a convenient inner class that contains all the information that
  needs to be kept between restarts.
o Store information in which key the notes are displayed in instance
  state.
o Make sure that a running game survives Activity lifecycle.
o Create random notes within selected major scale.
  (the entirely random note sequence is not _that_ useful).