When you have two guitars tuned alike you also experiment with the phenomenon of resonance or sympathetic vibration. If you pluck one string on one guitar, and the second guitar is just a short distance away, the second guitar's similar string and only that string will sound softly and mysteriously without being plucked.
~Mary Ellen Bowden & Theodor Benfey writing in "Robert Burns Woodward and the Art of Organic Synthesis"Nancy Duarte wrote a fascinating piece about resonance and public speaking here. She wrote:
The audience does not need to tune themselves to you—you need to tune your message to them. Skilled presenting requires you to understand their hearts and minds and create a message to resonate with what’s already there. Your audience will be significantly moved if you send a message that is tuned to their needs and desires. They might even quiver with enthusiasm and act in concert to create beautiful results.We have a real dissonance coming out of Washington D.C. We have public figures and radio personalities demanding that we tune to their frequency, rather than the other way around. We are not a captive audience.