Adding subdued music to iMovie videos that does not drown out conversations

Yes. Select the video clip (by clicking on it) in the time line, that is above the audio clip. Click on the loudspeaker icon in the tool bar in the upper right of your screen. Check the box that says "lower volume of other clips". The volume of the audio clip will decrease, as seen by a dip in the wave forms. Wherever you move the video clip, the audio clip beneath it will diminish in volume for the duration of the video clip.

You are most welcome. :)

-- Rich