While checking a grassy field that sometimes hosts breeding Grasshopper Sparrow, I heard I call that I was completely unfamiliar with. It can be heard twice in this video—once near the beginning, and then again when there's less noise and it can be heard fairly clearly. The call has three distinct parts...1) a brief series of chirps, 2) a whistled "fwwEEE-ooo" that is repeated once, and 3) an extended "churrrrrr" that kind of peters out. Please note that I am not an experienced ear-birder and this could be a very common species.
https://www.youtube.com/watch?v=srg_ae-P2KE&feature=youtu.be
https://www.youtube.com/watch?v=srg_ae-P2KE&feature=youtu.be