This puzzle is reminiscent of the old TV game show "Concentration". In the show, matching two tiles would reveal part of a rebus that had to be solved to win the round. Here, answering a clue correctly will show part of a rebus which is actually a question. Solve the fifteen clues first to expose the entire rebus, solve the rebus and finally answer the rebus question. If you feel that you've solved the rebus and can answer it before it's entirely exposed, send me a PM with your solution.
All answers are between seven and eleven letters long and are formed from the letters that makeup the word "concentration". No letter duplications allowed. So, if your answer has two a's and there's only one "a" in "concentration", your answer is wrong and you will be subject to a swift lashing across the knuckles with the proverbial ruler! See the puzzle grid
-1. it can be musical or mathematical
-2. a home network perhaps
-3. musical arrangement for an orchestra
-10. "about" or "including" could be words for this type of cryptic clue
-15. word with "time" or "chain"