The original owner is entitled to an Access Code that allows them to download the current version of Cubase AI (Advanced Intergration) - this is a special entry level version of Cubase prepared by Steinberg specifically for Yamaha products. It is provided to introduce Yamaha gear owners to world of music production with a computer.

It has more features than the Cubase LE (Light Edition), specifically in the area of audio integration and routing. With an S90 XS you will be able to record/playback MIDI data. You will need to get an audio interface, if you which to record audio to your computer.

The S-series will be able to record/playback MIDI data via a USB connection to a Mac or Windows computer.
With an external audio interface you'll be able to connect the Main L&R Outputs of the S90 XS and have it send audio into your computer, and to your studio monitors. Audio interfaces range from small format mixer types to full fledged multi channel formats.

You'll need to contact your regional Yamaha distributor, (plead your case, as second owner), I cannot speak for every location, but they maybe able to get you an Access Code so that you can experience the world of computer based Music Production. The reason it is provided is to whet your appetite and one you get started you can (at a very cool discount) upgrade to the a more full featured version.

Do the upgraded version do more? You bet
Do you need to move to the upgraded version? That is to be determined by you.

The contact info for your regional Yamaha office is found in the very back of your Owner's Manual.

Good luck, if you have further questions, post back here.

Thank you Bad Mister.

If I need an audio interface, I can go for the Steinberg UR22MKII or UR242 (and keep it in the Yamaha family).

Both of these interfaces come with Cubase AI and LE with the purchase.

Other than the obvious additional inputs in the 242, does anyone know why I should go to the 242. I doubt I will ever be needing more than the 2 inputs at any one time.

Once again, thanks for the note back.

The reason for getting more than two inputs is not limited to just how many items you are going to record at once, but also consider how many devices you want to hear simultaneously.

Here's what I mean, say you record the S90 XS as MIDI Tracks to Cubase, and then want to add a vocal or acoustic guitar overdub. If your interface has just two inputs, you will need to disconnect the keyboard to accommodate the new input device. Now monitoring playback of the S90 XS becomes problematical because Audio must be returned by the S90 XS hardware. This will mean you'll need to render the S90 XS' MIDI Tracks as Audio prior to recording /overdubbing via your audio interface.

This is not really a major thing - because rendering audio before overdubbing additional tracks is a viable workflow - but just want to be sure that you know what you are in for, if you opt for just a 2-in audio interface.

Hope that helps.