Disclaimer: I am not a lawyer and this is not legal advice.
Long story short, “…a participant in a private conversation may record it without “eavesdropping” because the conversation is not the “discourse of others”, meaning that in Michigan (a “one party consent” state) you do not need all parties consent to record a conversation.
From the WikiPedia article:
Michigan courts have ruled that eavesdropping only applies to: “a third party not otherwise involved in the conversation being eavesdropped on”. This is because the law uses the wording, “the private discourse of others”, rather than the wording, “the private discourse of others or with others”. Michigan law is often misinterpreted as requiring the consent of all parties to a conversation.
From language in citation #32, a case in 2003 further confirming a ruling in 1982:
Initially, we note that eavesdropping is not at issue in this case. MCL 750.539c prohibitseavesdropping but that prohibition is limited by subsection 539a(2) to overhearing, recording,amplifying or transmitting the private discourse of others without the permission of all personsengaged in the discourse. The statute does not define “discourse,” but its ordinary dictionarydefinition is “communication of thought by words; talk; conversation; . . . any unit of connectedspeech or writing longer than a sentence.” Random House Webster’s College Dictionary (1992),p 384. Thus, “eavesdropping” is limited to overhearing, recording, amplifying, or transmittingthe private, oral, or written communication of others without the permission of all personsengaged in the communication. For that reason, a participant in a private conversation mayrecord it without “eavesdropping” because the conversation is not the “discourse of others.”Sullivan v Gray, 117 Mich App 476, 481; 324 NW2d 58 (1982)