DK-Chaos: I should have said it had to be level 71 or greater. In order for the repel to work, you need to have a pokemon at a higher level than what you're trying to repel. And no, running into Moltres has nothing to do with the pokeradar. It's a roaming legendery.
And regarding my speculation on the purpose of the fast tempo pokeradar music (I proposed that it might signify a boosted chance for a shiny patch like that of a chain of 40+)... if it were true, I predict that the music should not appear once you have a chain of 40+. In the past few days I have reset the radar at least 250 times while at a chain <40 and got the music five times. However, last night I finally reached a chain of 40 and reset the radar 165 times, and did not hear the music once while I was at 40+.
In addition, once I reached a chain of 40, I found a shiny patch after 20 resets. However, the following 145 times did not produce any shiny patches. It has been suggested elsewhere that shiny patches only appear once per chain. My observation offers a small piece of anecdotal evidence to support this suggestion.
While my notes are focused on chaining for shinies, I hope they are mechanistic enough for the purpose of this thread.