MOTM

a) when I think Mylar caps, I think those radial green ones from the 70s.

b) Mylar was the first available film caps, put they are generally pretty 
crappy.

c) the metallized polycarbonate caps (AVX/Thompson 'yellow box') are OK for
'lo fi' apps. The ECQ-V caps I use for LFO timers which are not critical 
(and
one can argue adds a slight variation, even).

d) they best sounding audio caps are ECQ-P polyproplyene and polystyrene.

e) on a side note: also avoid ceramic disc caps. Use axial AVX 'SpinGuard' 
or
the Kemet C410C series. 10x more reliable, better all-round specs.

Paul S.