I have traced the problem a little further; it will not do a mono
output, but is Ok with a stereo orchestra.  I guess that means it is
OK for testing, but this is a problem.
  I also suspect that with ALSA there is insufficient control over
output devices.  The ALSA implementation in csound4 used a fixed ALSA
device name (csound-dev I seem to remember) in preference to default,
so one could direct the audio stream via .asoundrc
  I have looked at the PA sources, and while there are many
environment variables, I cannot see how it relates to the .asoundrc

Another data point of the problem; on my main machine I have an
M-Audio DiO 2496, which is a stereo digital in, stereo digital out,
stereo analog out but the driver is a 12 in, 10 out setup as it is the
same chip and driver as M-Audio 1010.  On this machine I cannot play
the same stereo orchestra which works on my laptop.  I conclude that
the pa/alsa setup is just not usable.  Is there anyone who understands
this area?

==John ffitch