It doesn't work that way. The XLR combo jack on the Scarlet is an analog audio input and MIDI is not. You would need an interface with a MIDI port/controller already on the device.

You could record the piano by using 1/4in cables from the piano to the XLR combo jack on the Scarlett but then it's an audio track no midi editing possible.

You might want to investigate the latency instead. Do you have the right drivers for the scalett and the midi interface. Did you try to better ajust the sync and performances via your recording software. There's some ajustements in Scarlett drivers if I remember. Scarlett usally don't have that much latency. I have the [[url=http://[/URL]="http://global.focus…"]Scarlett 8i6[/]="http://global.focus…"]Scarlett 8i6[/] which I use to drive midi to a sound module while using a edirol midi interface to drive a click track and use a drum sampler. It was all ok.. Read hear about the latency problems.

It's likely that the latency between playing a key on the piano and hearing the sound is not primarily due to the interface. There will be latency caused by Cubase having to interpret the MIDI information and then generate the sound you have asked for, and often this delay can be larger than any hardware delays.

I have on occasion recommended people who are suffering genuine hardware latency problems with MIDI to use a USB MIDI device instead of the MIDI ports on their audio interface, as USB can be a faster way in to a computer than having to go through the device drivers associated with the interface. Since you are already using a USB MIDI device, unless it's only USB 1.0 it will have about as low a hardware latency as you can get.

On another occasion, I took the keyboard's headphone output via an insert cable to two inputs on an interface and recorded the waveform output as well as the MIDI. In the DAW you could see and measure the latency, and a reasonable (but not perfect) correction could be achieved by sliding the MIDI data forward in time to compensate.

In your case, you could try monitoring the keyboard through its analog (headphone) output, thus not getting the MIDI transfer and synthesis delays during tracking. Unfortunately, I think the Scarlett 2i2 does not allow you to blend incoming signals with replayed computer signals when monitoring - you get either one or the other. So it may be a matter of trying to find or borrow a simple analog mixer to combine the headphone output from the keyboard with the monitor output from your interface. The audio quality of the mixer doesn't matter as it is never recorded. When tracking the keyboard in this way, either have the MIDI track monitor muted in Cubase or (better) don't synthesise the MIDI sounds. You still may need to time-advance the MIDI data track a little for the mix or for replay during subsequent tracking of other instruments or vocals.