Little handheld devices meant to record audio seamlessly, primarily for the purposes of dictation. Technical information is mostly unknown, but ARM, MIPS, or RISC chips may be what these often feature.

n/a

Remember that some voice recorder does not support high Bit Rate so some issues could be

Not exactly an EOP of operating systems, but various ones of this line can become an mp3 player with some simple swaps of files.

https://hacklab.cz/2013/09/03/hack-voice-tracer-digital-recorder-mp3-player