Here's the sE / Rupert Neve RN17 small-diaphragm condenser on upright bass, using an unorthodox (but very cool) mic technique. A few tips from the session's engineer, Frederik Brandt Jakobsen:
"This way of recording double bass sometimes works and sometimes doesn’t - it really depends on the sound of the instrument, and the musician playing it. I personally feel that I get the most natural sound of the instrument this way. By placing it here, I can slightly boost or attenuate the frequencies as desired: if I want more low-end I’ll position it lower, but for more high-end and string sound I’ll go higher with the microphone. With a very clean and good condenser like the RN17, you achieve such a completely natural balance between the strings and the body of the bass."