One must understand that music theory is not dependant on any particular instrument.
Instruments rely on dexterity of finger or breath etc. and therefore a great deal of expertise is acquired by practice of manual finger work or breath to deliver the self same musical science that pertains to all instruments.
So it could be what ever instrument takes your fancy from seeing things on tv etc or your hero,s on the musical scene.
I like the logic of the piano key board or electronic synth keyboards .But I also very much love the vibrations of the classical/nylon guitars for learning the ear work.