I manually dropped the ball into the boomerang 7x last night to see. It does award 100k and makes a sound, but not the tune I was referring to, and def said "100K" but without the word "bonus", and was awarded on the spot. Whatever does what I am referring to is a totally unique sound and was either 99k or 999k "bonus" and awarded at the end of a ball and in addition to and after the regular bonus. I think I am going to go thru audits and check sounds and see if that tune comes up and what it is labeled as.... maybe that will tell us.
Or maybe I am mistaken and it is just the total bonus and plays the song because you maxed it out... like I said, I have only done it 2x maybe 3x in over 2 years. For whatever reason I thought it was an additional bonus after the regular bonus.