an 'a-ha!' moment: according to one of the musicians who played under Mahler, Mahler told another musician who had complained to him about his peculiar, hard-to-follow beat that a conductor is, quote, "a necessary evil". That's a line that I get beat up for using quite frequently, but it's true. Now I have it from the horses's mouth.
. . . "lots of vibrato and glissando"
That is interesting because the non-vibrato advocates more or less argue that glissandi were used in lieu of vibrato. Here we get both.