Instrument Block

 The instrument block consists of a number of 16 byte records. The exact
 number of records can be found in the CMF header. Each record gives FM
 characteristics for each instrument as follows :-

 ──────────┬────────────────────────────────────────────────────────────────
   Offset  │  Usage
 ──────────┼────────────────────────────────────────────────────────────────
    00     │  Modulator sound characteristic
    01     │  Carrier sound characteristic
    02     │  Modulator scaling/output level
    03     │  Carrier scaling/output level
    04     │  Modulator attack/decay
    05     │  Carrier attack/decay
    06     │  Modulator sustain/release
    07     │  Carrier sustain/release
    08     │  Modulator wave select
    09     │  Carrier wave select
    0A     │  Feedback/Connection
   2F-33   │  Reserved for future use
 ──────────┴────────────────────────────────────────────────────────────────

 Sound Characteristics
   Bit 7     │ Pitch Vibrato (AM)
   Bit 6     │ Amplitude Vibrato (VIB)
   Bit 5     │ Sustaining Sound (EG-TYP)
   Bit 4     │ Envelope Scaling (KSR)
   Bit 3 - 0 │ Frequency Multiplier (MULTIPLE)

 Scaling/Output Level
   Bit 7 - 6 │ Level Scaling (KSL)
   Bit 5 - 0 │ Output Level (TL)

 Attack/Decay
   Bit 7 - 4 │ Attack Rate (AR)
   Bit 3 - 0 │ Decay Rate (DR)

 Wave Select
   Bit 7 - 2 │ All bits 0
   Bit 1 - 0 │ Wave Select (WS)

 Feedback/Connection
   Bit 7 - 4 │ All bits 0
   Bit 3 - 1 │ Modulator Feedback (FB)
   Bit 0     │ Connection