  Frequency mixing processes in spin systems have a variety of applications in
meteorology and in quantum data processing. Spin spectroscopy based on
frequency mixing offers some advantages, including the ability to eliminate
crosstalk between driving and detection. We experimentally explore nonlinear
frequency mixing processes with negatively charged nitrogen-vacancy defects in
diamond at low temperatures, and near level anti crossing. The experimental
setup allows simultaneously applying magnetic driving in the longitudinal and
transverse directions. Magnetic resonance detection is demonstrated using both
Landau Zener St\"uckelberg interferometry and two-tone driving spectroscopy.
The experimental results are compared with predictions of a theoretical
analysis based on the rotating wave approximation.
