Made famous by George Costanza as you can see the clip here, the answering machine song may seem like a good idea. It's out of the box, unexpected, and definitely a novelty, but unless you're in the music business, it's probably not a good idea. You'll definitely irritate your mother (or anyone else important who calls you frequently) and you won't make a good first impression with your message.
Informal voicemail greetings are those that don’t adhere to the rules of professional and business voicemail greetings. Here, you are free to just leave a simple greeting, or use it to show your more witty side. This style of greetings can be used for both home and business if you like, depending on the type of caller you expect. For instance, a novelty shop could probably create a rather informal message, using sound effects that represent the type of items they sell.

The first time you tap Voicemail, you’re asked to create a voicemail password and record your voicemail greeting.
If you have a main business phone number that’s shared with the customers or publicly listed, you’ll want to make sure it has a professional voicemail message to greet callers. Here are sample greetings you can use to help you craft your own.