On second thought, listening, and memory, I realized that the calls are of a totally different sparrow then the sighting. THe calls, upon recalling a sparrow I spotted near the calling site, came from smaller, duller sparrows without the striking white and yellow supercilium. In fact, on these sparrows, the face was as dull as the body, but the song was remarkable. I cannot find a recording that matches, although Song Sparrows sound close and I even heard in the background of one recording some Red-winged Blackbirds calling, which is just what occurred on my walk.
The larger sparrow that I spotted was much further down the trail in different habitat - more wooded. Looking in my field guides, there's nearly no doubt in my mind that it was a White-throated Sparrow, whose call is not at all like those near the marshy pond.
I also noticed that the Chipping Sparrow call is very similar to that of the Pine Warbler. Not that I doubt my Pine Warbler IDs, but I can see where that'll quickly pose problems now that I see the Chipping Sparrows around.