1. that's because you're not using real instrument.
2. Different instruments have to be transposed to a different key otherwise it won't sound right because they play in a different key and they only have a certain range.

That's the problem when writing music with a program when you don't know music theory.

You should get the guitar playing rhythm, then piano riffing/soloing in the same key - or vice versa. You don't want any instruments playing the same thing, it does work it just doesn't sound pleasing.