I really like the sound these toy keyboards make, it uses low quality PCM samples, which means there is some noise present in them, but they can really add an interesting flavour to your productions.
The SA-21 is cheap and has a headphone jack so you can record it using an interface.
WAY bigger 1's & 0's for that thick, creamy digital sound. Much bigger 1's & 0's than anything else out there.
Grabbed it at a Goodwill ages ago cuz $7 bucks. Life, funny as it is- We had our regular keyboard crap out on us & played about 15 more shows on that tour with the Casio...and ya know? It did kinda sorta ok? We definitely had to play to what the Casio can do & included a few pedals & embrace the campy nature of the Casio.
After a late night drinking session & with my wife asleep I recorded a song with guitar, bass, the Casio, and a LOT of pedals all going direct & I still love that song. I used the crazy campy drums on the Casio as well as a few keyboard patches. Super fun.
Do I plan on touring with it again? NO WAY. It was & is fun to play with but even in the "toy" keyboard arena I have a few others that are just way more fun. So this guy really doesn't see a lot of action anymore but it'll likely stick around anyway. If you find it cheap? Yeah, why not I guess.