I think we've never discussed this one. This is an obscure Soviet era Russian home computer from 1983, one of earliest here. Actually a range of computers, kinda like ZX48/128 series. It is a 16-bit system, based on the LSI-11 architecture. It has extremely ugly graphics, much worse than CGA (imagine that), and of course no sound hardware besides our beloved beeper. Later models like BK-0011M had 128K, disk drive, Covox and AY-3-8910 hooked up, mostly borrowed from Spectrums of the era, but these are minority.
The platform wasn't much popular, always being in the shadow of ZX clones, but it had a following nevertheless, and was one of the second-popular platforms at demoparties. As it is not even remotely compatible with any game computer in existence, all software was created by its enthusiasts. A lot of stuff, from graphics to ideas, has been borrowed from other platforms, including ZX Spectrum. There are some impressive efforts, too, like, Prince of Persia and Monkey Island ports.
To my knowledge, there is a reasonable amount of beeper music. Mostly ripped from ZX Spectrum games, however, with engines rewritten into PDP-11 code, so the sound is much different. There is some original stuff, too, including a couple of music editors with multichannel engines. I would guess that it is the third beeper-heaviest platform after ZX and Apple II, by the sheer amount of stuff.
One problem is that there isn't much videos on YouTube. One can use an emulator (there is a few) and use this archive. Another one is that nearly everything you can find about this platform is written in Russian, so you're going to need a translator. For now a couple videos for you, hopefully will dig out and post some more.