The Audio Tropf is a unique creature. It is a symbiotic creature that lives inside your head, feeding off of sound waves picked up through the ear canal. It's waste product is an electric signal that, consequently, tells your brain to release endorphins; which is why we feel happiness while listening to music.

When an Audio Tropf enters you, it establishes a psychic link. when that link is broken, (usually meaning the host is dead) it leaves the host.

Different Tropfs enjoy different combinations of sound waves, which is why different people enjoy different music and sounds.

When an Audio Tropf picks up a sound it does not like, it releases a signal to your brain telling it to feel pain and/or discomfort.

The "eyes" you see are really its ears, or the equivalent of.

An Audio Tropf is practically immortal. It can only die because of accidents, or malnourishment. Reproduction is a huge mystery with these things. It's believed that they reproduce a-sexually, but that's still being debated.