You can execute a reset of all MIDI notes by changing the position of the Voices toggle-switch in the upper-right corner of the main GUI-window. The position can be changed back after notes are reset. The change must be done manually: switching between programs that happen to have different Voices-toggle positions does not perform a reset.
Because of the synthesis method and the focus on sound quality, Shepherd can use higher amounts of CPU than other plugins. If you want to reduce CPU usage, these are some parameters worth considering (be aware changing these values can impact how the Shepherd sounds):
Unison: controls the number of notes played for each MIDI note. Lower values reduce CPU usage.
Voices: controls the number of notes able to be played simultaneously before note stealing occurs. Lower values reduce CPU usage.
Sub-Period Mixer: if you don’t need sub-period mixing, then turn it off. When on, the sub-period mixer will use less CPU if the frequency ratio (or its reciprocal) between Osc1 and Osc2 is an integer.
Modulator use also adds up. The more assigned modulations, the higher the CPU usage.