Squeeker Plus - ZX Spectrum music beeper engine
by utz 07'2016
1tracker version by Shiru 01'2018


A four channel engine based on original Squeeker by Zilogat0r, with many 
new features. 

The engine provides four channels of tone with detune support, 
customizeable step based envelopes for duty cycle. Channels 1 and 2 
feature an additional noise mode, channel 4 has slide down effect. Two 
click drums. 



Instrument editor tab (F4) allows to edit duty cycle envelopes. 

Envelope length can be set up to 64 steps. It can be made longer by 
using Duration different than normal, it can be Double or Triple, so a 
16 step envelope will last 32 or 48 steps. 

Each step of envelope can be set to a level that affects both tone and 
perceived volume. Higher level gives fat loud sound, lower level makes 
the sound thin and quiet. 

There is 9 predefined envelopes (can be edited too). Instruments 1..8 
has fixed duty cycle ranging from fat to thin, instrument 9 has duty 
cycle slide down. 


	
The columns are:

Sp T1 dEnN T2 dEnN T3 dEn T4 dEnS D
.. ....... ....... ...... ....... .
   |     | |     | |    | |     |
   +-ch1-+ +-ch2-+ +-ch3+ +-ch4-+
   
Sp : Speed, 1..99

T1,T2,T3,T4 : Tone channels, each has a note, detune, envelope number,
              and an optional channel-specific parameter
			  
   Tn : Note, C-0..B..7
    d : Detune, 1..9
   En : Envelope number, 1..99
    N : Noise mode for channels 1,2. Different notes will produce
        various kinds of metallic and noise sounds
	S : Slide down mode for channel 4. Slide speed is fixed.
	
 D : Drum, 1 kick, 2 snare
