You can read RCW 9.73.030 (Intercepting, recording, or divulging private communication – Consent required – Exceptions) to see what you propose to do is governed by the statute. The statutes can be accessed here: http://apps.leg.wa.gov/RCW/default.aspx?cite=9.73 .
You can read the opinion of the WA Supreme Court in STATE v. TOWNSEND, 147 Wn.2d 666, 57 P.3d 255 (2002):
The subjective intention of the parties to the communication is among the factors that the court may consider in determining if a communication is private. A court may also consider other factors bearing on the reasonableness of the participants' expectations, such as the duration and subject matter of the communication; the location of the communication and the presence of potential third parties; and the role of the nonconsenting party and his or her relationship to the consenting party.
I believe Washington like Illinois and California's laws prohibits the recording of "confidential communications" unless all parties to the conversation consent.
See my Legal Guide Recording Conversations in Illinois
You need a lawyer because I do not practice in WA (I am in Chicago, IL). Check with a lawyer in your locale to discuss more of the details. I agree with the observations of Mr. Thuong-Tri Nguyen.
Good luck to you.
Again, check with a lawyer in your locale.
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