FlatBass was part of my early experiments with drum samples. It’s not a drum instrument, it’s a sort of bass, obviously.
The idea was, I sold the drum sampler instruments outright, but you’d download the free FlatBass and get it to work in your DAW. If you could make that work, then you would probably be fine buying the drum sampler instrument as that was installed in the same way. That was the idea, anyhow!
FlatBass is a funny instrument, because it’s designed to be tiny. It’s very nearly a soundfont, looping its samples really obviously. I guess you can get a sort of organ-bass thing out of it? Anyhow, FlatBass is old and odd and free, and if anyone enjoys it that’s all I would ask. Electric Bass is somewhat better, instrument-wise, and also free.