povver - ZX Spectrum beeper music engine
by utz 11'2016
1tracker version by Shiru 12'2017


povver is an experimental 3-channel beeper engine. It features a simple 
volume control mechanism which is achieved through dual oscillators 
running with a phase offset. The results are perhaps not as impressive 
as what can be achieved through digital multi-core synthesis, but it 
consumes much less RAM. 


- 16 levels of volume
- Simple volume envelopes
- Noise mode for channel 1
- Customizable click drums
- Per-row tempo control
- Compact music data format



The columns are:

Sp T1 dENVo T2 dEVo T3 dEVo DKpNv
.. ........ ....... ....... .....
   |      | |     | |     | |   |
   +--ch1-+ +-ch2-+ +-ch3-+ +drum
   
Sp : Speed, 1..99

T1,T2,T3 : Tone channels
   Tn : Note, C-0..B-7
    d : Detune, 1..9
    E : Envelope, 1 to enable. Makes a quick envelope slide down.
	N : Noise mode, 1 to enable. Available for ch1 only, different
	    notes will produce various metallic and noisy sounds
   Vo : Volume, 1..15
   
DKpNv : Drum channel
      D : Drum, 1 kick, 2 high hat, 3 low hat.
     Kp : Initial kick pitch, 1..99 (lowest to highest)
     Nv : Hat volume, 1..99 (lowest to loudest)
