User blog comment:KressKross/Does Weiss actually sing?/@comment-24072355-20140806091054/@comment-24072355-20140806101346

They still might, the was I see RWBY is it's still early days.

also when it comes to her humming she may later loosen up character wise, perhaps singing is merely an outlet she hasn't fully established yet.

Practically speaking though Kara (awesome lady) is the voice actress for Weiss and I don't know about her musical ability, Casey (another awesome lady) is the one who sings in the white trailer's "mirror mirror" (and all the RWBY female vocals) and she would need to be specifically asked and arranged a sound booth recording specifically for humming, which is probably a bit too much work for humming.

Still perhaps later we'll have 'Weiss' singing again