Yeah, you're right. I just stared at the Dover score now. But I can also see why Robert Shaw did what he did (and everyone else played "monkey see, monkey do", I guess).
The altos in Choir I are already at fortissimo on the third line (ascending) Bb. Interestingly, the sopranos in Choir I don't enter again until their forth space "C" at rehearsal 213 ("Alles vergaengliche"). The sopranos and altos in Choir II have the same third line Bb as the altos in Choir I (the "aaah" part of "hinan"), but they started piano, and have a "molto crescendo" marking that ties over to 213, where they suddenly shift up a step to the fourth space C (and thus, the Choir I sopranos join them at that point). You're correct in saying that there's no marking for a hold or pause, unless the source of the Dover score had simply left it out (which is the sort of thing that happens with scores ALL of the time).
Perhaps what Shaw was trying to do was make that crescendo sound more obvious. Although, the Choir II sopranos/altos would be battling against the Choir I sopranos, who are already singing fortissimo. Or, even more likely, is that Shaw was simply wanting to make it obvious that - while there isn't a key change at 213 (Alles Vergaengliche) - the tonal center pretty much goes up one step for everybody at that point. If that's truly the point, then I applaud putting in a slight hold on the Bb, because it makes the "Alles Vergaenglich" part - which is a big, fat Ab chord (so that the "C" is the third in the chord) - sound that much brighter against the previous, mostly Eb chord that ends the "hinan" part.
But more troubling to me, is how the "terraced" effect of the ending gets missed on so many recordings. Mahler makes it very clear that there's a separate harmonium part - separate from the main organ. At 213 - "alles vergaengliche" - it's the main organ there, marked fortissimo (a hugely spread Ab chord), and with the added words "volles werke". Do you hear anything even remotely like that on most recordings? You certainly don't with MTT (and at least Boulez does have a separate harmonium). Anyway, when you reach the final "hinan" in the chorus, there's a forte tam-tam smash there (forte; fortissimo isn't until later); the pipe organ enters at fortissimo, and the offstage brass enter at that point.
Well, several things are interesting about 218 and beyond. First off, the offstage trombones have three part harmony there. Do you ever actually hear that? Frankly, all of the offstage parts should get doubled, and - therefore - not get placed too close to the onstage brass. But here, Mahler writes one of his markings that actually leads to more problems than solutions: he makes the comment that the first trumpet part can be doubled ("mehrfach besetzt). So, what often times happens, is that you hear a lot of the first trumpet part, but little of the harmony underneath them (and the trumpets have three part harmony as well). If you do this right - as the score says to do - you should be hearing a lot of the organ chord, and lot of harmony from the offstage brass. Just before 219, which is where the two sets of timpani and suspended cymbals do their "thang", the onstage brass answer the block chords that the offstage brass are playing at that point.
Now, here's what's truly interesting: the pipe doesn't reappear until 220 (the harmonium has continued to play on), which is where the tam-tam has it's second forte stroke (not fortissimo), and Mahler suddenly marks "Pesante". This is the spot where both Chailly and MTT put in their break, and it's a really bad spot to do that UNLESS you really crank up the organ at that point - the organ joins the harmonium at 220. The strings also enter fortissimo there, not that you can actually hear them. Anyway, at 220 (the second tam-tam smash), the pipe organ plays a big, fat Ab chord (with an Eb in the bass), fortissimo, with Mahler again saying "volles werke". Folks, he frickin' wants some organ there!!! That second tam-tam smash is also doubled by a bass drum roll (marked mezzo forte), which you don't hear at all on the new MTT recording. Then - and here's the clincher - when we get to the third tam-tam smash (the first one that's doubled by the cymbals, and the offstage trumpets do their ascending leap of a 9th), the bass drum roll is supposed to be fortissmo. At that same spot, the timpani start their rolls at piano, and make a crescendo all the way to the very end.
When you look at the score, you'll see all these "terraced" layers that you simply don't hear on many, many recordings. For example: four measures from the end, the onstage trumpets and trombones enter the sustained, already saturated Eb chord with full harmonization. Then the offstage trumpets join them two measures later, which is two bars from the end. Absolutely nobody has a crescendo marking here, except for the timpani, as everyone should be playing fortissimo already. The very final note is marked triple forte for everyone, except the strings (they have fortissimo). When you look at this, it's no wonder that the MTT M8, and a host of others (he's not alone), sound rather underwhelming.
