How to do it?

MUSIC FILE FORMAT v1.0

• Header (16 bytes):
  • +0: [2] Magic: “SD” ($53 $44)
  • +2: [1] Version (1)
  • +3: [1] Flags
  • +4: [2] Tempo (ms per row)
  • +6: [1] Number of instruments
  • +7: [1] Number of patterns
  • +8: [1] Song length (orders)
  • +9: [7] Reserved

• Instrument Table (8 bytes each):
  • +0: [1] Waveform (WAVE_xx constant)
  • +1: [1] Pulse width / duty cycle
  • +2: [1] Attack
  • +3: [1] Decay
  • +4: [1] Sustain
  • +5: [1] Release
  • +6: [1] Default volume
  • +7: [1] Reserved

NOTE: This might support sample playback later. Waveform can be 0x10 to indicate sample? Address can be in +1, +2, +3, followed by volume envelope, speed, effects and (reserved) remains intact.

• Order List (1 byte each):
  • Pattern numbers in playback order
  • Terminated by $FF ($FFFF or $0000?)

• Patterns:
  • Each pattern is a sequence of rows
  • Each row is a sequence of channel commands
  • Row terminated by $00
  • Pattern terminated by $FF (see above)

Command Byte:

• Bits 7-6: Channel (0-3)
• Bits 5-4: Command type
• Bits 3-0: Depends on command type

OR

• Command Byte
• Channel Byte
• Data Word + Data Word + Data Word (Reserved)

Command Types:

• 00 = Note On (3 bytes total)
  • [Cmd] [Note] [Instrument]
• 01 = Note Off (1 byte)
  • [Cmd]
• 10 = Set Volume (2 bytes)
  • [Cmd] [Volume]
• 11 = Effect (3 bytes)
  • [Cmd] [Effect Type] [Effect Param]