I I have the Chick Corea Samples from the Yamaha Premium Collection and I'm trying add the equivalent of the Rhodes Tremolo effect but I can't find anything like Tremolo amongst the MOXF8 effects. can it be done?
I assume you want to add tremolo to the voices themselves, as opposed to adding tremolo to a song.
See page 6 of the MOXF6/MOXF8 Reference Manual:
LFO (Low Frequency Oscillator)
As its name suggests, the LFO produces a wave of a low frequency. These waves can be used to vary the pitch, filter or amplitude of each Element to create effects such as vibrato, wah and tremolo. LFO can be set independently for each Element; it can also be set globally for all Elements. LFO related parameters can be set in the LFO display (pages 33 and 45) of Voice Common Edit or Voice Element Edit.