In the beginning I refered to the web site mentioned below to solve the problem.
http://www.k13i.com/~koya/notepc.html
I'd like to express my appreciation to the web site mentioned above. It is, however, written in my native language, Japanese so you might need to use something like a translator, such as Google translate but I will
describe the gist of its content and support you in solving the problem.
The problem was that the error message "alsamixer: function snd_ctl_open failed for default: No such device" was shown on the screen and that alsamixer wasn't available on Debian 5.0 when we
started alsamixergui with YMF-744B. This might be because the firmware for YMF-744B wasn't installed and because the DFSG adhered to a strict interpretation of FOSS.
According to the web site mentioned above, we need to go to ALSA project homepage,
http://www.alsa-project.org/main/index.php/Main_Page
and download alsa-firmware-1.0.20. After then we need to install alsa-firmware. The command lines are given below.
# tar jxvf alsa-firmware-1.0.20.tar.bz2
# cd alsa-firmware-1.0.20
# ./configure
# make
# make install
# alsaconf
After configuring ALSA through alsaconf, we could confirm alsamixer was available on Debian 5.0.
Finally, I will be happy to assist you in setting up alsamixer with YMF-744B on Debian 5.0.