Wolf Resonator Cello E-F# (High)The wolf note resonator works on the principle that it counters the frequency of the cello body with its own frequency. This little device consists of a small block of lead suspended on thin bronze springs. Since wolf notes occur at different pitches on different instruments, various dampers are needed low notes d to e, middle notes e flat to f and higher notes e to f sharp. Supplied with complete fitting instructions, but we suggest that you have it