As of Furnace dev99, the following sound chips have sample support:
- NES/Ricoh 2A03 (with DPCM support and only on channel 5)
- Sega Genesis/YM2612 (channel 6 only; but only if there exists a `1701` effect that gets played on or before a trigger for a sample, or if you are using an instrument with Sample type)
You can actually tweak your samples in Furnace's sample editor, which can be accessed by clicking on `window` (at the top of the screen) then clicking on `sample editor`.
In there, you can modify certain data pertaining to your sample, such as the:
If you have a sample you wanna use that is about 44100 or anything over 32000Hz, downsample the sample to 32000Hz so that the pitch of the sample in Furnace stays like the original audio file. You can do this in Audacity by going to the bottom left of the screen (If you see "Project Rate (Hz)" you are there), change the project rate to 32000Hz and save the file to wav in Audacity using "File -> Export -> Export as WAV".