Around western Washington, in my experience, Black-throated Gray and
Townsend's songs are usually quite distinct. I have made sonograms of
recordings I've made here (but please don't ask me to send copies as it
would take me a couple of hours to make one) of both and by direct
comparison the Black-throated Gray song is a slightly ascending series of
ca. 5 burry notes while the Townsends' begins with a burry jumble but ends
with ca. 3 "brighter" clearer high notes. Hermit's and Townsend's X Hermit
hybrids further confuse the picture. I have, however, heard (and recorded)
"aberrant" Black-throated Grays that sound like anything from a Nashville
Warbler to a House Wren! Since they learn their songs there's always the
possibility they will imprint on some neighbor by mistake, I guess.

Gene Hunn, Seattle, hunnhome at accessone.com