Just wondering is there any way to get a stereo image in via keyboard while using the backing tracks. 

Lets say in the first instance I layer a bass pattern for a song then save that.

Can I get a stereo in via the Cd in and layer a keyboard/synt track over that?

Im looking basicly at the spider jam as a solution for both bass and keyboard amp but it would be great if I could use the featuers with my keyboard as well as bass guitar.

Would an alternative to put one track in via the guitar in and one via the aux in (left and right channels from keyboard/synth).

Thanks for the help so far .