Tina,
 
> tim,
> line 3:
> "my surrounding air hath a new lightness;" (because I have left her
> lately. ie. I feel 'lightness' because I am on my own).
 
"I have left her lately" = I have just now been with her. The word "lately"is
being used in a somewhat archaic sense here, not in the way we would
use the word today in modern American idiom. We might say "lately I've been
getting up at the crack of dawn", meaning for the past week or couple of
weeks.
But in the sense in which it is used here, lately means a time very close to
the present:.
"just now" or "earlier today" or "just last night".
 
He is still smelling her perfume and is entirely "wrapped up" in the
experience
of having been with her -- it is not a poem about the experience of breaking
away from a former lover whose love has become confining...though it is
perhaps a rebuff to another whose love cannot compare.
 
> then:
> "slight are her arms, yet they have bound me straitly" (she binds me
> 'straitly.' I don't have a dictionary here but straitly seems
> negative--like her arms are slender (pos.), YET she binds me straitly).
 
That is, she held me close and tightly though her arms were slight (did not
look very strong).
 
> do you think the poem is based on anything else? I was reading an old
> issue of paideuma in which an article related various poems in ripostes to
> romanticism (esp. Keats).
>
 
This rhetorical device, where opposites or seeming opposites are yoked
(slight...yet strong),is common in renaissance poetry.
 
> what do you think is the significance of the title?
 
The virginal was a popular instrument during the renaissance. It produced a
delicate music,
more delicate than the harpsichord, because it had only one string per note.
It is the musical
analogue to the "gauze of aether" and the "subtle clearness",  a symbol of
this lady herself.
 
Tim