LMan / Remix64 wrote:AFAIK, c64 manages 4-bit only, cause the volume register has 4 bit.
Not really true. You can do higher-bit sampling by using pulse width modulation and careful timing of the processor, but this locks the computer completely and it will do nothing else than playing the sample. This produces a high-pitch noise from the root frequency of the pulse, but in the background, you'll hear that "more-than-4-bit"-sample.
Anyway, it's lo-fi, however you twist and turn it!

The best result you'll get from sampling it with any PC, and then write your own C-program to normalize it, dither it and properly encode it so that your handwritten assembly-loop will play it nicely! That's a lot of work, but also a lot of fun!
The highest "frequency" that has been done using pulse width modulation is around 1 sample per rasterline (63 clock cycles on a C64 @ 1MHz), which is somewhere around 15kHz.
Anyway, I certainly don't know everything that has been done on this earth, so if anybody knows more, please tell!