You can’t. It’s an audio effect, not a virtual instrument. What you can do, is take the sound of a keyboard patch and process it with Guitar Rig.
In respect to this, can I make my guitar sound like a piano?
The quick answer is that to truly make your guitar sound like a piano, you can either buy a Roland GR-55 Guitar Synthesizer with a GK-3 pickup, a Fishman TriplePlay Wireless MIDI Guitar Controller, or even an Electro-Harmonix Key 9 Electric Piano Machine Pedal.
Consequently, can you use guitar rig with MIDI? GUITAR RIG is not a sound generator (such as e.g. MASSIVE or KONTAKT) but a virtual guitar amp and effects processor. This means that you need to feed GUITAR RIG with an audio input signal. You can control its parameters via MIDI but it does not produce sounds itself.
Keeping this in view, how do I make my guitar sound like an instrument?
How do you make a MIDI foot controller?
How do you play guitar and piano together?
How do you use a guitar rig?
What happened to the harpsichord?
By the late 18th century the harpsichord was supplanted by the piano and almost disappeared from view for most of the 19th century: an exception was its continued use in opera for accompanying recitative, but the piano sometimes displaced it even there.
What is a MIDI foot controller?
Midi Foot Controllers are mainly used to switch guitar amp channels, changing effect settings or controlling your complete guitar rig.
What is Rig Kontrol?
The Rig Kontrol 3 is a high quality foot controller designed for use with the NI GUITAR RIG software. It offers a built-in high quality soundcard and is also a preamplifier for electric guitar and bass.