> where in his Concerto for Orchestra does the Shostakovich parody
> appear? thanks.

The fourth movement is entitled "Intermezzo interrotto" (interrupted
intermezzo). It begins with a gentle play lead by the oboe, in an
irregular rythm. Next the violins play a sentimental melody (it's also
a free quotation of a Hungarian song: "My beautiful Hungarian
country"), which is also in an irregular rythm. The oboe play comes
back. Here comes the quotation: we hear a somewhat vulgar theme, with
a regular binary dance rythm. It's like some vulgar people would come,
laughing about serious things (the laughing is indeed illustrated).
When they went away, the two other themes come back, in an "astonished
" manner.

The vulgar theme is not only a quotation of the Shosta symphony, but
it's also a quotation of a theme from Lehar's "Merry widow" operette.
Bartok's theme resembles both of these themes.