The interesting thing is that the original SS7 code did not have an arbitrary case programmed for the ring back tone; that is to say the original network infrastructure did not support on-demand changes to ring backs or to pull an arbitrary media file at the time of call. The solution was a box intermediating the call to stream musical media before connecting to the actual intended voice call media.
Telecom, why do stuff in softwhere when you can just add another box?
I can't think of an actual need for that ability, only the fact it could be used for novelty, abused to annoy people, or just flat out cause problems (i.e. what if my ringback tone is a busy signal?)
My father used to take the handset off the hook during important family meetings. Anyone who called during that time got a busy signal. This was long before ringback tones were a thing.
I've also heard of a similar technique being used to fight telemarketers a few years ago. Many telemarketers run a program that automatically detects nonexistent numbers and removes them from the list. So this guy made an app to imitate the phone company's 404 error msg (or whatever the audio equivalent is) whenever he received a call from a known telemarketer. I don't know whether he did it with a ringback tone or just played an mp3 after picking up, but anyway, he no longer received any calls from telemarketers after a while.
When you call a person with a RBT there is first a message saying "If you want this tone for 10cents please press 7", then the music starts, usually the latest chart-song.
Needless to say it has a solid customer base made up mostly of teens, but also of corporates with a company jingo as the RBT (I kid you not).
Im not sure if the big chat apps (will dominate VoiP) have this function built in yet but Id imagine they will at some stage, a nice VAS if you can charge for it..
One day several years ago I noticed the number of calls I was getting was going down. Then one day a friend texted me asking what was wrong with my phone, I asked what he meant and he said it had stopped ringing when ever he called me and all it did was play music now. He was rather confused, and I was just as confused but skeptical too, I requested no change in service. I asked him to come over to demonstrate and sure enough there was a song that would play whenever someone called me. I figure most people thought that meant some kind of error and hung up, most of the time before it hit my phone.
I called my carrier and angrily complained and the poor woman tried to pass this off as a service, but I was having none of it. I demanded that they disable it immediately and I apologized to friends and family who were confused by it. Nearly switched carriers over it as well, this is preposterous IMO and was executed with very little forethought.
Shortly afterwards, ringbacks disappeared entirely and I was all the happier for it. I get the sense there are multiple lessons to take from that anecdote.
Ring Plus is still working with that technology - but now does a lot with reverse ringback tones; rbts based on what you want/prefer to hear, not what the person you're calling wants you to hear. It's now a mobile phone MVNO in the U.S using reverse RBTs to deliver a Spotify/Rdio/Pandora-style radio feed that goes towards subsidizing or eliminating your phone bill.
