Thank you for your reply!
If I do plug the Casio to the Solo as you said, would I need a software such as Ableton with a Library of its own then? I am not sure I really understand the advantage with the setups storing for recording with the Solo, would it make it possible to get the sounds from the Casio at all?
And is Casio selling the mono cables with two conductors that you mentioned?
I know about the recording options but my (few) attempts to use it failed. (I actually managed to record and listen to the recordings while using the keyboard but somehow failed to put them on the SD card, I must try again.) that is why I was asking about recording directly through my usual sound card onto my computer. The amount of options and technical aspects is a bit overwhelming, especially for someone new to sound material like me. ( So far I used the paper manual I received with my Casio, but using the online manual in my native tongue (French) in the future probably won't hurt either!)