To any conversation there are only ever two parties. If you are participating then you are participating at that moment by talking to one of the others. But you cannot record a conversation where two or more others than yourself are talking.
I disagree with that premise. A conversation certainly can include more than two people. Suppose Amy, Becky, and Carl are talking together about last week’s football game. While only one person is talking at a time, the other two are listening and participants to that conversation. i.e. there are three people to that conversation. So, under federal and NJ law, if Amy wanted to record that conversation, she could do so legally. And not just the parts of it in which she talks, as you seem to suggest. If I understand correctly what you are saying, I find it very bizarre.
So in my hypothetical, if Amy addresses a comment about the game to both Becky and Carl she is not communicating to both of them? If that is the case, with which one is she communicating? How would you, as a communication major, sort that out? If it is a “fact” (i.e. something you can test scientifically) that one can communicate with only one other person at any one time, please give me a citation with the proof of that. I did some Google searching and found plenty of references to communications involving more than two people but none, not one, that asserts that all communication is strictly limited to two people, and only two people. So forgive me, but I am not going to accept your word on this one just because you say you have a communication degree.
Let me at least give a citation to back up my view. The book Effective Business Communication breaks down communication into intrapersonal, interpersonal, group, public and mass communication. The latter three all involve communication involving three or more people. That discussion has citations to other authority for its definitions. You can read that here: http://open.lib.umn.edu/businesscommunication/chapter/1-3-communication-in-context/
So, do you disagree with that discussion? And if so, what authority do you rely upon that supports your view?
In any event, it is clear that the law allows Amy in my hypothetical to record the discussion among Amy, Becky, and Carl about the game and not just Amy’s own speech.
New Jersey recognizes the defense of vicarious consent for minor children, with the case law centering on concerns of physical abuse, but that's not carte blanche -- if somebody is not a party to a conversation, they should refrain from recording it. If somebody believes that vicarious consent may allow them to record a conversation involving their minor child and another person, even a parent, they should discuss the facts and case law with a lawyer. "I'm recording lots of conversations in which I'm not a party because I think there is some verbal / emotional abuse" sounds to me like recipe for disaster.
As a basic matter of logic, I find the premise that a participant in a conversation isn't "participating" unless somebody is speaking directly to them (at which time they must scramble to hit the "record" button), they are answering, or somebody is responding directly to something they said, to be unsupportable. I have not seen any court in any part of the nation apply that sort of interpretation of what it means to be a participant in a conversation -- instead, courts treat it as a binary. Further, given that many of the cases involving recording by a participant in a conversation involve recordings made by undercover police officers and informants, were such a rule applied the case law would be overflowing with arguments about whether the recording started or ended a second too soon, or how the recording can only be understood in the context of the unrecorded material.
New Jersey law provides,
Quoting N.J. Stat. Ann. Sec. 2A:156A-4(d)
I met with two lawyers on my impending divorce case about this topic. As if it wasn't complicated enough, one lawyer said flat out it's illegal. He didn't want to hear my reasoning, even when I suggested NJ was a one-party consent state. The other lawyer, who was more intimate with my case and going a bit beyond the first lawyer, said it's absolutely legal as long as I'm a party to that conversation. He also said if another person was in the conversation I couldn't record it if it wasn't a conversation between me and him (so him and the other person). My concern is being wrongly accused of abuse, harassment, etc. and getting arrested if my wife wants me out of the house while we go through divorce. Covering my ass is really important.