Question about function generator's arbitrary waveform generation ability
Maybe. Depends on the unit. Basic units allow playback of one waveform at a time. This means that you could construct an arbitrary waveform with two frequency components and play it back, but you could have issues with repitition if the frequencies do not share a common factor. More advanced units can add two or more waveforms together on the same output port. One of these will definitely do what you want.