Analysis of Harmonics

This string upon my harp was best beloved:
I thought I knew its secrets through and through;
Till an old man, whose young eyes lightened blue
'Neath his white hair, bent over me and moved
His fingers up and down, and broke the wire
To such a laddered music, rung on rung,
As from the patriarch's pillow skyward sprung
Crowded with wide-flung wings and feet of fire.

O vibrant heart! so metely tuned and strung
That any untaught hand can draw from thee
One clear gold note that makes the tired years young--
What of the time when Love had whispered me
Where slept thy nodes, and my hand pausefully
Gave to the dim harmonics voice and tongue?