Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Filename
GV_SOUND_FILENAME
Parameter: Probe
GV_SOUND_PROBE
Parameter: Play
GV_SOUND_PLAY
Parameter: Time
GV_SOUND_TIME
Parameter: Sample
GV_SOUND_SAMPLE
Parameter: Left
GV_SOUND_OUTPUT_LEFT
Parameter: Right
GV_SOUND_OUTPUT_RIGHT
Parameter: Length
GV_SOUND_LENGTH
Parameter: Samples
GV_SOUND_SAMPLES
Parameter: Bands
GV_SOUND_FFT_RES
Parameter: Band
GV_SOUND_FFT_BIN
Parameter: Left Mag
GV_SOUND_FFT_BIN_LEFT
Parameter: Right Mag
GV_SOUND_FFT_BIN_RIGHT