Not sure why my comment merited a downvote. In any case, quoting from Mass law:
https://malegislature.gov/Laws/GeneralLaws/PartIV/TitleI/Cha...
The term ''interception'' means to secretly hear, secretly record,
or aid another to secretly hear or secretly record the contents of
any wire or oral communication through the use of any intercepting
device by any person other than a person given prior authority by
all parties to such communication.
The term ''contents'', when used with respect to any wire or
oral communication, means any information concerning the identity
of the parties to such communication or the existence, contents,
substance, purport, or meaning of that communication.
If you get content, useful or otherwise, from the recording, you are violating the law. Unless you fall under one the exemptions, which you probably don't.
So first question, "devise a mechanical device" -- violates. Second, "write notes", no. Third question, "secretary record" -- no.