The new ftconv manual is attached. Also, here is some preliminary
documentation for GEN52:

f # time size 52 nchannels channel_params_1 channel_params_2 ...

where each channel_params consists of three values in the
following order:
   * source ftable number
   * start offset (can be negative, any samples beyond the range
     0 to source table length - 1 are assumed to be zero)
   * read location increment (can be zero to repeat the same sample
     indefinitely, or negative to play backwards)
GEN52 creates an interleaved multichannel table from the specified
source tables, in the format expected by the 'ftconv' opcode.
It can also be used to extract a channel from a multichannel table
and store it in a normal mono table, copy tables with skipping some
samples, adding delay, or store in reverse order, etc.

Example:

; source tables
f 1 0 16384 10 1
f 2 0 16384 10 0 1
; create 2 channel interleaved table
f 3 0 32768 -52 2 1 0 1 2 0 1
; extract first channel
f 4 0 16384 -52 1 3 0 2
; extract second channel
f 5 0 16384 -52 1 3 1 2

Note: these manuals apply to the latest developer CVS sources, and
are not compatible with the current Win32 file release.