I think the light reads very bad.

I don’t like the "webfonts" facility at all, so far.

Thanks for the feedback. After trying upwards of ten similarly shaped, differently weighted typefaces, I'm pretty happy with the overall weight of the page when the typeface is on the light side.

Mostly, I think that with webfonts the problem is: they should have been designer for screen.
The first and foremost think which hinders legibility is having not enough overall space. Lato is spaced tightly, and the lighter weights, they just give an headache to anyone which has even minor unease with reading onscreen. This, of course, goes for smaller point sizes.

Why not use Myriad?

The Light sans webfont look is very interesting. Cutting edge, even.
But it is out of place in this layout.
If you are going to use sans for this kind of subject matter, you have to go totally modernist, as if performing classical music in a brand new concert hall.

Thanks for the feedback, everyone. I'm willing to take another look at heavier weights—I just felt the whole page got to looking too heavy, but I'm not an expert and would like to broaden my experience.

Nick, one of the things I'm most interested in is the way classical music is portrayed, and that includes typography. I want the subject matter of the site to appear ordinary and normal, so I don't want to go the New Music route of highly noticeable sans serif typefaces. (I'm a graduate student in composition, and I get enough of that in my conservatory.)

I have no budget, so I'll look at the Myriad lookalike CartoGothic. Any other suggestions are highly welcome! Thanks! :-)

You need to add some space between the lines. By then, a regular weight won't look so horrible. Be sure to double check Win XP rendering! Most web fonts break under those conditions.