DEMOS MADE FOR ZX SPECTRUM 48kb
You should keep in mind that Spectrum's native sound-source - Z80 chip - is also the computer's CPU. Therefore - like ZX fans used to say about BEEPER demos - "When music is playing, scroller must stop".
As You will see, there is not too much movement on da screen in BEEPER demos while music is playing: it's because almost all CPU's powers (3,5 Mhz only!!) go for music-procedures.
This problem hasn't appeared in demos for ZX48K + AY interface because AY works in interrupts and doesn't requires too much of CPU's power (while chiptunes play anyway).
That's why BEEPER demos are mostly music-collections (might
be mixed with slideshow etc...) whereas demos for AY are much more attractive in
their visual side.
DEMOS FOR ZX48K + AY interface BEEPER demos (sound generated by Z80)
INTROS 256b, 512b, 1K, 4K, 16K CLASSIC demos (80s or early 90s)