I have grown up with Corn Buntings calling outside of the house and in the surrounding countryside, so their call is a very familiar sound to me; you can hear it for yourself in this short video - https://youtu.be/riNOWIGumPU
In 2005-6 I studied calling male Corn Buntings intensely for my BSc dissertation project, surveying 100 square kilometres in North Lincolnshire, England, finding over 150 calling male Corn Buntings. I recorded their song post and crop selection of where those song posts were situated coming up with some very interesting observations. Umbellifers such as Cow Parsley were selected over all other song posts with a very high level of statistical significance which was contrary to casual observatiosn that suggest that man-made posts and overhead wires are mostly chosen. These song posts were important in my survey but it is likely that because Corn Buntings calling from these posts are very easily seen, a false impression of their importance for calling Corn Buntings comes across. I would add, though, that comparison to other literature on Corn Buntings it is obvious that each population can have different behaviours. My findings on umbellifers have been confirmed in other UK Corn Bunting populations and some farmers have sown these plants in conservation borders with some success for Corn Buntings.
The other finding of my study was less surprising; the greater the crop diversity, the more Corn Bunting territories it sustained. What was perhaps a little surprising was that this also applied to very small variations in crop diversity, for example two bordering wheat crops that were planted at different times and so had different stages of growth.