Different coloration than last one (tentatively Neduba steindachneri) found in same vicinity last month. Haven't found any photos that come close to this coloration. Similar song, but slower (perhaps due to lower temperature, rather than due to species?), usually 13 rasps in a row, like running fingernail along teeth of a plastic comb. I think he's gorgeous. :>)
CLOSED: another species of shield-backed katydid?
Definitely appears to be Neduba; possibly (and I stress the possibly) Neduba sierranus - confirmed images of males (as yours is) of this species appear few and far between. Try listening to recordings of Neduba steindachneri at http://entnemdept.ufl.edu/walker/buzz/140a.htm and Neduba sierranus at http://entnemdept.ufl.edu/walker/buzz/150a.htm to see if that helps.
Thanks for the audio links. They are much better quality than what I've been able to record.
The N. sierranus recording on the ufl.edu site sounds close to my first creamy-colored "chickadee" katydid; I haven't heard anything here yet that's as harsh as their N. steindachneri recording.
Here's a link to my recordings, in case they're any help: https://drive.google.com/file/d/0Bz7yDUlb-UrhcXNUTS01S0ZiWVU/edit?usp=sharing
The N. convexa photo on the ufl.edu site is mottled grey with mottled reddish shield, like my second katydid. The photo of Aglaothorax diminutiva also has similar coloration. But on bug-guide.net, N. convexa pictures are creamy with dark markings. Is coloration not as indicative of species in Neduba as some subtle morphological characters?
Also, I'm wondering if the blurry photos I initially took of my "chickadee cricket" are a third species, as it seems to have a central dark stripe that the clear pictures lack any hint of.
Just be aware that individual specimens within any given species may vary considerably in color pattern, and that microscopic examination of certain body parts often is necessary to make a species determination. I suggest that you contact the entomology department at Oregon State University for their opinion - http://www.science.oregonstate.edu/bpp/insect_clinic/index.htm
OSU entomology was able to get them IDed down to Tettagoniinae, and no farther. I'll try posting on bugguide.net.