Hi,

These are implemented in Gardner Reverbs on my web page:

http://www.werewolf.net/~hljmm/csound/

The nested all-pass filter opcode is in progress, it's taking me a while to
get around to it.  The form is something like:

aout  nestedap  ain, imaxtime, imode, itim1, igain1[, itim2, igain2, itim3,
igain3]

Hans Mikelson