Actually, I had only installed alsa-lib prior to mpg123. I noticed that alsa-lib did NOT put any default *.conf files anywhere so I:
cat > /etc/skel/.asoundrc <<"EOF"
# Begin .asoundrc
cp /etc/skel/.asoundrc /root/
Which may not have necessary. Then I continued on to build alsa-plugins & alsa-utils according to LFS 7.2 instructions and mpg123 just started working. Now I have sound on my LFS machine, its on to X11 ...