Riddle (Piano)

I am a grand thinker
I've played my part in greatness
If you press me for an answer
I will tell you
I am a work of endless joy
Of passion and possibility
Countless combination
Infinite imagination.
I am made of pieces that make pieces of pieces
As you see, I am very playful
Though sad, and serious
A wonderful communicator
My personality shines
Even in a darkened room
My life is one of lows and highs
Brilliance and melancholy
I see the world in black and white
But have a heart of gold.
I am a creature of no words
A zebra-coloured song-bird
With feet, but cannot walk
Scales, but cannot swim
A crazy exhibitionist
Accompanying the lonely
With tone but little colour
I move others
But cannot move myself
Unless my insides dance.
People write for me, though I cannot read
People read from me, but I am no book
I have a seat, but am not a chair
Open and close, but am not a door
I have a lock with many keys
One voice, many voices
I may lift you (even to tears)
Though you could never lift me.
I have hidden depths, and hidden heights
I adore the limelight (which is drawn to me)
I am alive with joy
A sequence of things
Amazing crowds
Exciting air
Brought to life by hammer and string
An arrangement
A tool
An instrument of love.
What am I?