Feedback from my friends:
"Did you do that on purpose?"
"I thought I was caller #9 at the radio station."
"That's effing weird"
"Was that rap?"
"I called your phone and the weirdest thing happened."
"That's weird"
"I thought I was on hold."
"I thought you were in a night club."
"I wasn't sure how long it was going to last."
(i.e., easier to count five or six rings)

And, I have to admit, many of my friends simply hung up without leaving a message.

My phone log:

Fri Apr 22 Ina 7:20 pm
Fri Apr 22 Ina 7:21 pm
Fri Apr 22 Ina 7:21 pm
(no message left)
Fri Apr 22 Belis 7:40 pm
Fri Apr 22 Belis 7:40 pm
Fri Apr 22 Belis 7:41 pm
(left a short, confused message)
Fri Apr 22 Richard 9:20 pm
Fri Apr 22 Richard 9:20 pm
Fri Apr 22 Richard 9:21 pm
Fri Apr 22 Richard 9:22 pm
(no message)
Sat Apr 23 Barnhart 2:30 pm
Sat Apr 23 Barnhart 2:31 pm
Sat Apr 23 Barnhart 2:32 pm
(message)
Sat Apr 23 Maricel 4:30 pm
Sat Apr 23 Maricel 4:31 pm
(no message)
Mon Apr 25 Alissa 10:42 am
Mon Apr 25 Alissa 10:43 am
(message)

You get the idea.

From those who observed/listened to the ringback once the concept had been explained …

"very cool. I want that"