Ni hao 
,
Well, the synthesizer can literally can come up with thousands of
unique sounds. Some of which you can record on your own. With the
introduction of MIDI (Musical Instrument Digital Interface) in the
80s, the process of music-making becomes a lot easier. Names like
Roland, Korg and Casio comes to mind. I own a 1990 Casio SHS-10, a
keyboard that was shaped like a guitar. It comes with only 44
voices and music accompaniments but more if I were to hooked it up
on a MIDI-compatible computer.
Nowadays with the internet, you can download loads of other sound
samples from the websites. I'm not sure which websites to go but
you can always Goggle my good man...
Zaician 
P.S. If you wish to get one for your band, may I suggest you go
around and look for a second-hand but well-maintained keyboard. New
ones can set you back - very expensive mind you, with so many
gizmos...