Stocker - ZX Spectrum beeper music engine
by Shiru 08'10, some inner loop improvements suggested by Alone Coder
1tracker version by Shiru 07'15



A powerful engine similar to the Music Studio 48K. Has been written to 
use in game Magic Tokens, music has been created with a converter from 
Vortex Tracker II format at first.

1tracker version has a number of changes and fixes, but the sound is 
still the same. 

The engine provides two channels of PFM tone controlled with 15 fully 
customizeable envelopes, similar to the volume ones seen in AY trackers. 
It uses 16-bit counters, supports detune, legato, slides up and down on 
both channels, and four types of interrupting click drums. 

To edit envelopes, use Instrument editor tab (F4).



The columns are:

Sp T1 dlEnSld T2 dlEnSld D
.. .......... .......... .
   |        | |        |
   +---ch1--+ +---ch2--+
   
Sp : Speed, 1..99

T1,T2 : Tone channels
  T : Note, C-1..B-5
  d : Detune, 1..9
  l : Legato, 1 to play this note as a legato one
 En : Envelope, 1..15
Sld : Slide, 1 down, 2 up, then speed 0..99

 D : Drum, 1..4
