So I originally was going to be releasing something earlier than the current date but it's been POSTPONED (postpwned?)! The reasons why aren't many but they are important.
Ever since RetroCopy was first being worked on and I was solving the problems that come about with a multi system emulator (MAME being another example of one) the issue of dealing with sound was one that bothered me greatly. Firstly you have to deal with PCs that aren't that too good at doing what emulators desire, and that is low latency, real time output of dynamic audio samples.
DirectSound is OK-ish at helping with this, but it's not ideal. At least once you know its flaws you can output audio at a decent quality using it (the same thing is easier said than done on other platforms). With the move to VISTA though the soundscape changed, and no longer was hardware acceleration possible, which isn't too big a deal for emulators but it introduces its own issues.
But the issue from an emulation viewpoint, is how do you take these analog sound chips found in the Nintendo, Genesis, Sega Master System, etc, and make them sound like they originally did on PC digital hardware? Well the sound chips are still mostly digital devices, and they have a clock rate, on each pulse of the clock they do something. So along comes the emulator and looks at what it does, sometimes on each clock (accurate) but more often on every few clocks (more inaccurate but faster).
RetroCopy has always looked at every clock for every sound chip it covers as it one of few emulators with a focus on accuracy. However where I haven't been too focused is what do I do with the samples I collect. You can't just take the sound from the chip and output it to the PC as they are at differing frequencies. The easiest way to do this is just to average or skip samples so that you can take the sampling rate of one device (the NES) and convert it to another (the PC). While the simplest it also introduces a few quality issues that many can notice.
So starting with the next version RetroCopy will have a very high quality resampling engine for every sound chip. It is likely one with the highest signal to noise ratio in comparison to any other emulator. It's a little slower than what I doing before but the improvement in quality is very noticeable. It is almost finished now, I just have to complete the NES sound chip.