Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is a fantasy dark comedy about the same eccentric morbid Addams Family we know from the old Charles Addams cartoons and the 1964 TV series. It stars Anjelica Huston, Raul Julia, Christopher Lloyd, and Christina Ricci, who also appear in the 1993 sequel "Addams Family Values." There is a brief scene with a crazy musical instrument that is made out of what is supposed to be a live snake. The Addams family's home is full of similar fantastic things, including a polar bear rug with a living head, a painting of a candle that gets extinguished, a servant that is a detached hand named "Thing," a book titled "Hurricane Irene" that unleashes a hurricane when it's opened, plants that attack people, and a front gate that opens and closes itself.
We see the snake instrument when the family throws a huge dance party for Uncle Fester. Gomez and Morticia are dancing to a weird waltz when the movie cuts to a close-up of a musician blowing into the tail of a snake and fingering holes along the snake's body which is resting on his leg with the snake's head elevated. We hear a reed instrument similar to an oboe, though the instrument is shaped more like a saxophone. When the musician blows, the snake opens and closes its mouth as the sound comes out. Another nice detail is that the snake has a hood like a cobra, but instead of the eye-like markings cobras have it is marked with old-fashioned lowercase "f' markings like the holes on a violin or cello. The snake also has two large fangs on the top front of its mouth, because all movie snakes have them. I'm tired of complaining about that. Later there is a full shot of the entire small orchestra, including the snake instrument. All of the other instruments look normal but the bass fiddle is fingered by a one-armed man and plucked by Thing.
The snake instrument looks like a practical effect and not CGI, but I'd like to know how they made the head move back and forth.