In most states, only one person needs to be aware that the conversation is being recorded. His conduct would have been completely legal in the majority of the US. [1]
It seems like 21 years is a very harsh sentence for conduct that isn't physically dangerous and isn't even illegal in the majority of the US.
I seem to remember reading or hearing somewhere that police departments actually like the rule used by most states, "recording is legal as long as at least one participant in the conversation knows about it." This makes gathering evidence in investigations a lot easier because you can record everything without a warrant. If we suppose the world consists of "criminals," "informants," and "police," and police and informants always know about their own recording devices, then criminal-to-criminal calls are the only case that needs a warrant in a state with one-party notification. Informant-to-criminal and police-to-criminal can legally be recorded without a warrant, probable cause, reasonable suspicion, or any basis whatsoever in such states.
[1] https://en.wikipedia.org/wiki/Telephone_recording_laws#Unite...
It can produce some oddities in companies as well. It's now assumed that a corporation can read employees' email, for example, or record their internet or IM traffic. But in a two-party-consent state, it would be illegal for your employer to record telephone calls made from your office phone, unless they get the consent of each person you talk to.
My understanding is that the most restrictive state applies, so you don't even have to be in a two-party state, you just need to be calling one.
In any case, this is why every call center you talk to says "this call may be recorded" when you first connect. It's not just a courtesy!