Most good halls are shoeboxes, but Orchestra Hall is egg shaped. The sound tends to travel straight up, and before the most recent remodel (late '90s), the Gallery, or top balcony, featured better sound than in most seats on the main floor, at about a quarter the ticket price. For the remodel, a large (and ugly) acoustic reflector was suspended over the orchestra. Before, the sound was dim and foggy in the balcony below the Gallery; it is noticeably clearer now, but at a cost. Because the reflector acts as a huge microphone, the sound is never really pianissimo even when the musicians are playing at the edge of silence, and in the Gallery it's generally harsh.
Part of the problem, I suspect, is that the hall does not contain enough cubic feet of air for a large orchestra, and if the musicians play too loudly, the sound can become a colorless sludge. Even at low and moderate levels, I've never heard a rich, mellow string tone anywhere in the hall, and that is not the fault of the players. The conductor really matters: Haitink has a knack for scaling the sound to the hall and his performances remain transparent even in the louder tuttis. I heard a night-and-day difference between M9s with first Barenboim, then later Haitink conducting. Under Barenboim the sound was a harsh grey haze, but that never happened in the Haitink performance.
Under studio conditions, recording companies had a fighting chance of showing the orchestra in a good light. But now that virtually all their recordings are live, the potential for decent sound is severely limited.
As for Muti, I've been to just two or three of his performances here, not because I'm trying to avoid him, but because he is often playing uninteresting repertoire. However, I think he a much more mature conductor than he was in Philly. In one concert I heard Haydn 101 (a work I love dearly), and was astonished by the quality of the performance, nor would I have guessed that Muti would show much affinity for Haydn. The program included "Feste romane," and sure, it's trashy, but the performance was terrific, with the orchestra in top form.
Then too, in Philly Muti showed an affinity for Berlioz that I find surprising. While the sound is admittedly thick and Germanic, allowing for that his recordings of "Symphonie fantastique" and "Romeo" are surprisingly idiomatic.
Finally, I heard M9 in last Saturday's MSO concert with de Waart. Excellent on all counts, though he did spoil Mahler's joke near the end of II when he slowed down gracefully rather than abruptly near the end. Locals tell me that the orchestra improved a lot under Andreas Delfs, and that de Waart brought it to a new level. The MSO has played superbly in a number of concerts I've attended in recent years.
And if that's not enough, they even seem to have upgraded their tamtam. Previously it sounded like a large cymbal, but last weekend it was atmospheric in the soft strokes and most powerful in the big collapse i I.