As is remarked away back in the Catalog 3 comments, this might be a reference to the condition synaesthesia, a sort of "crossing" of senses, where an auditory stimulus can cause a visual sensation. There are some synaesthetic artists, inspired to paint an impression of what they see when hear a piece of music, for example. In view of the fact that there is also a Catalog 3 track called "Visual Drone 12", this is the view favoured by [DC].
Alternatively, it could be taken literally - I saw drones, as in unmanned aerial vehicles. However, this usage of this term was fairly rare in popular culture at the time.
Additionally, drones may refer to male bees. Unlike the female worker bee, a drone has no stinger. He does not gather nectar or pollen and cannot feed without assistance from worker bees. His only role is to mate with a maiden queen in nuptial flight. This could also be an allusion to the phrase "the birds and the bees," a talk parents are expected to have with their children.