1
general::
In complete accord, in rapport, as in Conductor, orchestra members, soloists, and chorus all were on the same wavelength, making for a wonderful performance. This term alludes to radio waves that carry a broadcast. [First half of 1900s]
American Heritage Idioms
2
general::
Phrase(s): on the same wavelength
Fig. thinking in the same pattern. • We’re not on the same wavelength. Let’s try again. • We kept talking until we got on the same wavelength.
McGrawhill's American Idioms And Phrasal Verbs