So the followup for Yamaha's P-95 is coming up and seems like it's an interesting piece of work.

I would love to know if it has AUX-IN connectors, so that you could hook up a computer or an MP3 player for play-along sessions. I have some backing tracks I would love to use with my piano.

Looking at the specs, I don't see aux-in on the P95 or P155 ... with any line-out keyboard, there must be some way to mix the keyboard's output with another source, and listen to both? In fact, run the DP to the computer line-in, and then it should be able to that automatically.

To do just that, I ordered a mixer to take both headphone outputs of the piano and computer. Headphone then plugs into mixer's headphone out.

What kind of mixer?

Like this: small mixer

or this line mixer

I have the line mixer because I have several old sound modules, but the small mixer or the next size up would probably work ok for you.

totally low tech buy I actually prefer to run earbuds for the backing track and earphones overtop with the piano sounds....sounds better to me that using the aux in and is easier to tweak the volumes for perfect mix.

I ended up ordering Behringer 1202 FX which cotains digital effect module with chorus, reverb and many more effects. Thanks for the tip.