Two modes of oscillation, L and S, associated with large and small plates were described, with frequency analysis by counter [A. Powell, J. Acoust. Soc. Am. 83, 515–533 (1986)]. With different slopes on log‐log plots of wavelength versus nozzle‐to‐plate spacing h, feedback to nozzle and to stand‐off shockwave, respectively, was hypothesized. Digital signal processing is more revealing! The same dominant and S tone are found, exactly. It now appears these L and S are the dominant members of classes of tones. At small h, for large plates (all pressures) and small plates (low pressures), L tones are observed in multiple modes, usually simultaneously. For intermediate h, frequency jumps occur; schlieren photography reveals symmetric and asymmetric jet flow oscillations. Nozzle reflector influence supports the feedback to the nozzle hypothesis for L. For large h at low pressures, three strong constant tones exist—screech a1 and a2—and one other(?). At higher pressures (small plates), S tones appear, influenced by a nozzle reflector (!); schlieren photographs exhibit symmetrical oscillations of jet and stand‐off shockwave. For intermediate plates, both L and S classes occur.