connection method: like web audio nodes, scenegraph hierarchy implicitly connects nodes
-- Benefit: source nodes can run in their own thread and each note has fine granularity timestamp
routing method: source nodes convert to route fields and destination nodes take route fields
-- Benefit: simpler implementation
-- routes are processed once per frame, and notes would have frame time stamp granulariy
Node design choice: connection method, with utility processing nodes converting to/from routes
Source and destination nodes: midi messages are routed directly 
  by implicit connections like web audio nodes by scenegraph
MidiDestination (MIDIPortDestination, MIDIFileDestination, MIDIOut)
    MidiSource  (MIDIPortSource, MIDIFileSource, MIDIIn)
Processing nodes are routed to/from MIDIIn, MIDIOut (MIDIToneSplitter, MIDIToneMerger, MIDIConverterOut, MIDIConverterIn)

source node: stop, start, pause, resume, rewind, loop
realtime source node: stop, start. Has no loop or rewind, stop and pause do same thing, start and resume do same thing, no content is buffered/saved when paused/stopped

Nodes needed for MIDI
Level 1:
MIDIPortSource : MIDISourceNode 
{
  <standard realtime source node fields>
  SFInt32 [in,out] port 		0
}
MIDIFileSource : MIDISourceNode
{
  <standard source node fields>
  MFString [in,out] url 		[]
}
MIDIPortDestination : MIDIDestinationNode
{
  SFInt32 [in/out] port 		0
  MFNode  [in,out] children 	NULL
}
MIDIFileDestination : MIDIDestinationNode
{
  SFString [in/out] url 		[]
  MFNode  [in,out] children 	NULL
}
MIDIPrintDestination : MIDIDestinationNode
{
  MFNode  [in,out] children 	NULL
}
Level 2:
MIDIOut : MIDIDestinationNode
{
  MFInt32  [out]    midiMsg
  MFDouble [out]    midiUmp
  MFNode   [in,out] children 	NULL
}
MIDIIn : MIDISourceNode
{
  <standard realtime source node fields>
  MFInt32  [in]    midiMsg
  MFDouble [in]    midiUmp
}
MidiToneSplitter : X3DMIDINode
{
  SFInt32  [in,out] octaveFilter	-1
  SFInt32  [in,out] channelFilter	-1
  MFInt32  [in]     midiMsg
  MFDouble [in]     midiUmp
  SFBool   [out]    C
  SFBool   [out]    Cs
  SFBool   [out]    D
  SFBool   [out]    Ds
  SFBool   [out]    E
  SFBool   [out]    F
  SFBool   [out]    Fs
  SFBool   [out]    G
  SFBool   [out]    Gs
  SFBool   [out]    A
  SFBool   [out]    As
  SFBool   [out]    B
  SFBool   [out]    pedal
}
MIDIToneMerger : X3DMIDINode
{
  SFInt32  [in,out] octave 		5
  SFInt32  [in,out] channel		1
  SFBool   [in]     C 		
  SFBool   [in]     Cs 		
  SFBool   [in]     D 		
  SFBool   [in]     Ds 
  SFBool   [in]     E 
  SFBool   [in]     F 
  SFBool   [in]     Fs 
  SFBool   [in]     G 
  SFBool   [in]     Gs 
  SFBool   [in]     A 
  SFBool   [in]     As 
  SFBool   [in]     B 
  SFBool   [in]     pedal
  MFInt32  [out]    midiMsg 
  MFDouble [out]    midiUmp
}
Level 3: 
MIDIProgram : X3DMIDINode
{
  SFInt32 [in,out] instrument		1
}
MIDIDelay : X3DMIDINode
{
  SFTime  [in,out] delay		0.0
}
MIDIConverterOut : X3DMIDINode
{
  MFInt32  [out]   octave
  MFInt32  [out]   key12
  MFInt32  [out]   key88
  MFInt32  [out]   keyPiano
  MFInt32  [out]   pedal	
  MFInt32  [in]    midiMsg
  MFDouble [in]    midiUmp		
}
MIDIConverterIn : X3DMIDINode
{
  MFInt32  [in,out] octave		5
  MFInt32  [in,out] channel		1	
  MFInt32  [in]     key12		
  MFInt32  [in]     key88		
  MFInt32  [in]     keyPiano	
  MFInt32  [in]     pedal	
  MFInt32  [out]    midiMsg
  MFDouble [out]    midiUmp
}
MIDIAudioSynth : X3DMIDIProcessingNode, X3DAudioSourceNode
{
  SFInt32 [in/out] polyphony 	10
}