Hello again, everyone, given that my soundcard is shot, I am going to need to pick up an audio interface. I would also like to grab a midi keyboard/ synth, but I was wondering if I'd be able to transition between that and my bass (through the interface) within the jam. AFAIK, there is only a possibility for one input.
Am I mistaken?

Thanks everyone!

Yes, jammr uses one input device only. Changing the input device involves disconnecting from the jam and going into the sound settings to change the input device.

But there are setups where multiple instruments can be played without changing settings:

You can play a bass guitar and a MIDI keyboard controller without switching input devices in jammr. This works because the MIDI keyboard controller does not produce audio, it just sends MIDI messages to a VSTi plugin you can load within jammr. There are many synth plugins available, including free VST plugins you can try.

You could also use a mixer, especially a USB mixer, to blend multiple instruments with jammr seeing just one input device.

Finally, some people use audio routing software like JACK or virtual audio cable software. This lets you connect sound card inputs and audio produced by other applications with jammr (as a single input device).

I recommend starting simple. There is a ton of stuff you can do with computer audio and various gadgets, but they don't all play together well. It can be expensive and frustrating. Best to take it step by step and see what you like.