In the Voluum, usually there is one LFO. You can turn on "duo" mode to get two LFOs. When this is done, the second LFO has its tempo locked to the first LFO (they use the same bpm, or MIDI sync clock), but you can set different waveforms, depth, tempo divisions, phase (between LFO1 and LFO2). Because these parameters can be modulated, you can do things like fade from one LFO to another by modulating the depth of both LFOs; or make the sound more simple or more complex as you fade one of the LFOs and keep the other constant -- lots of possibilities.
You can get the Voluum user manual from here:
http://www.sonuus.com/products_voluum_docs.html