Here's a box diagram for a simple example, a smus with two instruments and
two tracks.  Each track contains 1 note event and 1 rest event.

                  +-----------------------+
                  |                       |
                  |   'FORM'        94    |  FORM 94 SMUS
                  |                       |
               -- +-----------------------+
               |  |                       |
               |  |   'SMUS'              |
               |  |                       |
               |  |  +-----------------+  |
               |  |  | 'SHDR'       4  |  |  .SHDR 4
               |  |  |-----------------|  |
               |  |  | 12800, 127, 2   |  |
               |  |  +-----------------+  |
               |  |                       |
               |  |  +-----------------+  |
               |  |  | 'NAME'      10  |  |  .NAME 10
               |  |  |-----------------|  |
               |  |  | 'Fugue in C'    |  |
               |  |  +-----------------+  |
               |  |                       |
               |  |  +-----------------+  |
               |  |  | 'INS1'      9   |  |  .INS1 9
               |  |  |-----------------|  |
               |  |  |   1, 0, 0, 0,   |  |
               |  |  |   'Piano'       |  |
          94  <   |  +-----------------+  |
         bytes |  |    0                  |
               |  |  +-----------------+  |
               |  |  | 'INS1'      10  |  |  .INS1 10
               |  |  |-----------------|  |
               |  |  |   2, 0, 0, 0,   |  |
               |  |  |   'Guitar'      |  |
               |  |  +-----------------+  |
               |  |                       |
               |  |  +-----------------+  |
               |  |  | 'TRAK'       4  |  |  .TRAK 4
               |  |  |-----------------|  |
               |  |  | 60, 16, 128, 16 |  |
               |  |  +-----------------+  |
               |  |                       |
               |  |  +-----------------+  |
               |  |  | 'TRAK'       4  |  |  .TRAK 4
               |  |  |-----------------|  |
               |  |  | 128, 16, 60, 16 |  |
               |  |  +-----------------+  |
               |  |                       |
               -- +-----------------------+

The "0" after the first INS1 chunk is a pad byte.