Pianist here chiming in -
xanakis - Unless you and I have two different definitions of chords, the piano is NOT the only instrument where you can play two true chords. Besides, if you can refer to a tonic, any two chords played together can be thought of as a single extended chord. Say I’m in C. My left hand plays a C major, my right plays a B flat major, which is, in this context a C11. If I play an E flat over it, I get a C7(#9) What’s your definition of a “true” chord?
As far as I know, a chord consists of any three different notes playing together. A guitar has six-strings, thus making two chords together possible, although usually they will be thought in the context of a single extented chord.
Here are your strings:
E A D G B E
Hold the third-fret on the low E, and the first fret on the low-A and you get:
G Bb D G B E
You can look at this as an Em chord over a Gm chord. Two different chords. Two true chords. More likely, you will analyze this as an extended G minor, G major, E minor or whatever, depending on the context. But the point is, you can play two different chords at the same time on a guitar, though your possibilities will be limited due to tuning.
Your hands do not have to be in two places at once to hit two chords. You can hit a chord on guitar without even having the left hand fretting.
Anyhow, you are also forgetting other issues with piano, which make it easier in certain ways, since it is a fixed-pitch instrument.
Remember, with violin, you only have four strings. Guess what? There are not frets, and you have to be spot on in teaching your fingers where the notes are. There is no F# key on the violin. You’ve got to find it. Then there is the issue of articulation. You now are open to a vast world of tonal embellishment. You have vibratos…you can make them slow or vast. You can speed them up or slow them down. You have a lot to practice on just getting your vibratos even. Then you can also glide up to notes or glide down. You have pizzicato; on the guitar you have bends, natural and artifial harmonics, a whammy bar occassionally.
With wind instruments you have most of these options plus you have to develop your embouchure (mouth shape.) From what I hear, this is a real pain in the butt.
So, speaking as a pianist, I would hesitate to judge an instrument’s difficulty by the amount of notes that can be played at any one time. To compensate, we don’t have to think about A LOT of tonal issues other instruments do.