There are almost always sound effects incorporated.
There is usually at least one silly voice. Variability in volume as well (Dad is of the school that finds whispering to be tremendous fun).
I called Dad on my way to school today because Edgar Winter Group's Frankenstein was on the radio. I was going to just let the song play into his voicemail if he didn't pick up, but unfortunately the song was over by the time it got to his voice recording.
So I hung up, didn't leave a message.
When Dad called back he did leave a message.
There were some beeping noises (his own) followed by some honking noises (ibid.). These were repeated for emphasis.
"That's the sound of two ships passing," he said.
Dad then explained that we too, like the ships, had crossed paths and that he was sorry he missed my call.
And then he said a prayer for me on my voicemail. Just asking God to be with me today, with whatever was going on. He also prayed for a good attitude for me--uh, yep. Need that one for sure.
I hope you understand now why I have multiple messages saved that I can't quite bring myself to delete.
(This doesn't even get us into my brother Patrick's messages, in a whole epic class of their own. His choice voices are usually foreign accents--most often Eastern European--and currently I have a saved message of him using a female voice, pretending to be his wife.)