// Uses Java calls to play notes via MIDI synthesis.  This requires a JVM that
// actually *has* a MIDI synthesizer (e.g. Oracle's JVM works,
// OpenJDK may not.)

synth = callJava["javax.sound.midi.MidiSystem","getSynthesizer",[]]
synth.open[]
chan = synth.getChannels[]

// This part is unnecessary but it shows how to change instruments.
soundbank = synth.getDefaultSoundbank[]
instruments = soundbank.getInstruments[]
instrument = rand[instruments]
patch = instrument.getPatch[]
(chan@0).programChange[patch.getBank[], patch.getProgram[]]

// Dump names of instruments?
for i=0 to length[instruments]-1
   println["$i\t" + (instruments@i).getName[]]

println["Random instrument for channel 0: " + instrument.getName[]]

sleep[1 s]   // Sound seems choppy if we play too soon?


// Major pentatonic scale
pentMajor = [0,2,4,7,9]    // I also see [0,2,5,7,9]
// Minor pentatonic scale
pentMinor = [0,3,5,7,10]

key = 60   // Start around middle C (these are MIDI note definitions)

simultaneousNotes = 3
lastNotes = new RingBuffer[simultaneousNotes]

for n=0 to 50
{
   keyChange = rand[[0,0,0,0,0,0,0,0,+7,-5,+5,-7]]   // Follows "circle of fifths"
   key = key + keyChange
   if keyChange != 0
      println["Key change: $key"]

   for note = 0 to 3    // Notes per measure without keychange
   {
      for sim = 0 to simultaneousNotes-1
      {
         mid = rand[0,10]
         // Play each note on a separate channel.
         note = key + (mid div 5) * 12 + pentMajor@(mid mod 5)
         if (length[lastNotes] > 0)
            (chan@sim).noteOff[lastNotes.pop[]]
         lastNotes.push[note]
         (chan@sim).noteOn[note, 93]
      }
      sleep[.5 s]
   }
}

sleep[9 s]  // Sleep while the notes play.