Can I use the audio input from a keyboard to generate harmonies using Harmony-G / XT?
The Harmony-G / XT pedal was designed specifically for guitar input triggering. The use of a keyboard's audio to trigger Harmony-G / XT is not recommended, nor has it been tested and proven.
The variance of the timbres that are possible using an electronic keyboard could give negative results.
The complexity of, say, string sounds, organ sounds or those with a lot of reverb and effects would prove difficult to translate. Harmony-G / XT concentrates on a pure guitar signal, as opposed to a keyboard signal which can have these varying degrees of clarity.