Thank you. Further testing leads me to believe that the problem is with PCem's emulation of the Ensoniq AudioPCI (ES1371). VMware apparently emulates the same type of card, and I can get sound working with ALSA using the "install alsa-config.tcz followed by alsa.tcz" process.
I did some tests in PCem based on your links. Using oss_alsa.tcz for ALSA emulation did get sound working, but it is spotty in the target programs.
Based on your third link, I tried alsaconf. Had to go back to version 5.x in order to find the extension; I used Core-5.1.iso for testing. alsaconf did find the card, and it generated this modprobe.conf:
# /etc/modprobe.conf: Modprobe config file.
#
# --- BEGIN: Generated by ALSACONF, do not edit. ---
# --- ALSACONF version 1.0.27.1 ---
alias snd-card-0 snd-ens1371
alias sound-slot-0 snd-ens1371
# --- END: Generated by ALSACONF, do not edit. ---
However, setup seems to have failed at the /usr/local/etc/init.d/alsasound step. I tried the command manually and got:
amixer: Mixer attach default error: No such file or directory
Something went wrong, sound was not set up. Since we are using the results of the last run of alsaconf make sure that your /etc/modprobe.conf file was properly backed up or has not been corrupted. You need to run alsaconf again or restore a working /etc/modprobe.conf.
alsactl init and aplay -l again gave the message about no soundcard being found.
The result of modprobe -r snd_ens1371 followed by modprobe snd_ens1371 had one extra line but still resulted in a failure:
snd_ens1371 0000:00:13.0: found PCI INT A -> IRQ 9
snd_ens1371 0000:00:13.0: setting latency timer to 64
AC'97 0 access is not valid [0x0], removing mixer.
snd_ens1371: probe of 0000:00:13.0 failed with error -5
I'll take this up with the PCem folks.