Mark Volpe and his organization pulled off an impressive feat in creating this season at such short notice. Former Music Director James Levine submitted his resignation only after most symphony orchestras, including the BSO, have established their programming for the next season and published it to waiting subscribers. Add to that the need to corral a feasible number of potential candidates for the open position of Music Director. The Boston Symphony’s 2011-12 is not only solid and nutritious, it is even rather exciting—apart from the added piquancy of the search. The fall will be mainly given over to guest conductors who have worked with the BSO for many years, or at least a few times in the past. The serious contenders for the permanent position will begin later on.