MixerGetLevel — Gets the level of a send to a buss.
Gets the level at which signals from the send are being added to the buss. The actual sending of the signal to the buss is performed by the MixerSend opcode.
isend -- The number of the send, for example the number of the instrument sending the signal.
ibuss -- The number of the buss, for example the number of the instrument receiving the signal.
kgain -- The level (any real number) at which the signal from the send will be mixed onto the buss.
This opcode reports the level set by MixerSetLevel for a send and buss pair.
Use of the mixer requires that instruments setting gains have smaller numbers than instruments sending signals, and that instruments sending signals have smaller numbers than instruments receiving those signals. However, an instrument may have any number of sends or receives. After the final signal is received, MixerClear must be invoked to reset the busses to 0 before the next kperiod.