The ongoing saga of running a beta release, I guess. Everything was pretty cool for 10 days or so, but then......
A few days ago, my laptop lost its voice. After doing some update or another, there was NO sound, except an occasional odd clicking noise when instead it should have been playing a music track. In KDE, one can test various sound devices and services in System Settings > Multimedia. This is also, by the way, where you see what backends are available to you, such as Gstreamer, Xine or VLC. This same window is used in Amarok to configure Playback > Phonon. Once sound disappeared, this configuration window in System Settings started crashing, so I filed a bug about that. Actually, it's still crashing, even now that I have sound back.
The nice part about filing that bug is that the crash handler AKA Dr. Konqui now asks you, if certain debugging packages would help display a more helpful backtrace, if you would like to install them. Then it searches the database, fetches the packages and installs them for you. Be sure to reload your report after the installations, of course!
Finally, I went over to Launchpad and filed a bug there about the sound issue, since my tests have revealed that this was a general problem, not a KDE one. https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/558910 if you are interested in this issue.
Salient points: aplay -l displays your sound equipment.
Of course first, I always checked Kmix. Often some channels were muted, but unmuting made no difference. I must have done that 20 times or so. I uninstalled Pulseaudio, which made no difference. I tried booting into next older kernel, still no sound. I used the TTY to run a sound file from Music123, which runs below X. It gave no error message; but appeared to be playing the file. No sound.
I also removed the phonon config in ~/.kde/share/config - no change. Rebooting into my original Kubuntu Lucid beta LiveCD, I heard sound again! After days. More updates, but still no sound.
In desperation, I asked in #unbuntu+1 (Freenode). The kindly folks there commiserated, and one person asked about Alsamixer. I remembered using it in opensuse, so I consulted my blog post here, and opened alsamixer in the console, and then used Ksnapshot to take a screenshot of it.
See where it says Speaker, and MM? Jordan_U kindly pointed out that that meant MUTE, and that I could change that by using the arrow keys to highlight the speaker column, and then use the M key to change to unmuted, which is 00 -- none of which makes any sense to me. However, sound now works! I updated my bug with the new information, because while my problem is solved, there is still a venomous bug, crawling around and biting random people!
Now I can get back to work in Amarok. Wonderful IRC people to the rescue once more! Thanks to Jordan_U and the rest of the helpful folks in #ubuntu+1.