This is a vary good question, and I'm sure any great arranger could answer it.
I'm no music expert or arranger, but I'll give it a try.
A tune is over arranged if the arrangement exceeds the skills of the players.
For example I'm sure Jit, Bradley or Boogsie won't give your local hometown steelband the same arrangenment that they'd give to their own signature, veteran bands.
A tune is over arranged if the arranger deviates from the tune such that the listener loses the feel and flavor original tune, and almost forgets the source melody.
Other than that I think the arranger goes where his instincts, his heart and his head takes him.
"A tune is over arranged if the arrangement exceeds the skills of the players." nah man never
Chris, I am in your corner on this one. For panorama, an arranger is working within the confines of a set time-frame. It is incumbent upon that arranger to fit as much music as possible into the time the criteria provides. Skill level of players should not come into the equasion. The players have a duty and responsibility to put in the time in the Panyard as required for them conquer that tune. The arranger has a vision of what this tune can be. It is the band's job to bring this vision to reality. When players approach panorama with this mind-set, the band's overall skill level improves rapidly.
In my opinion I would say u are wrong and right. because many arrangers stray badly from the theme but still keep my interest in terms of creating their own . That is where the term "through composed" comes in to play.But but pan competitions or competitions on the hole deal "theme and variation"
Interesting view points guys. There are several arrangements I listened to recently and always felt like the "musicalness" was "too much." I know this would be a sticking point for many, because persons can easily conclude that I am simple minded, or non-musical, or do not know how to listen to blah, blah blah...
But honestly, there are certain elements in arrangements that always will make a listener go "oh yes" or "dat nice" or "ya hear dat" etc. etc. etc. Most of the time when those comments are made, the music at that point is always VERY SIMPLE. Crowds love SIMPLE and SWEET...scholars understand complicated...also, simple + sweet does not mean mediocre. Look out for arrangements that achieve simple and sweet without being mediocre...