within the "Wavetable" tab of the instrument editor, Furnace allows you to modulate or combine 1 or 2 waves to create unique "animated" sounds. think of it like a VST or a plugin, as it's basically an extension of regular wavetable soundchips that still allow it to run on real hardware.
this is accomplished by selecting a wave or two, a mode, and adjusting the settings as needed until you come up with a sound that you like, without taking up a load of space. this allows you to create unique sound effects or instruments, that, when used well, almost sound like they're Amiga samples.
unfortunately, on some chips like the HuC6280, you cannot use the wavetable synth to animate waveforms and have them sound smooth, as the chip resets the channel's phase when a waveform is changed while the channel is playing. on certain frequencies, this can be avoided, but not on most, unfortunately.