Spincad is really helpful with a Spectrum Analyzer. Great for viewing filter changes. Exporting audio from Spincad is really easy and helpful but exporting doesn’t allow hearing the knobs tweaks. When exporting spincad mutes audio.

Voxengo is an awesome audio plugin for this reason.
https://plugins.landr.com/en/product/voxengo-span/

Couple things you need though.
Reamp Box – I made mine homemade for under 40 bucks, but they run about $100+. Really easy, just solder a few components https://youtu.be/xR3LqemYXOU
Audio Interface with at least 4 outputs and only need 1 input I use Motu M4.
Any Audio DAW program should work, I use Ableton
Spincad app https://github.com/HolyCityAudio/SpinCAD-Designer/releases

Connect reamp box to the secondary output, typically 3 and 4- I just use 3 with a TRS to mic cable
Connect reamp box to input of DAW, I use input 2
Open Spincad set audio to go to soundcard
Window Sound settings, set to secondary output of DAW, mine were 3-4
Run DAW make sure secondary outputs are activated
Assign the input from reamp box to audio track , may have to tweak input levels.
Enable monitoring on track and you should be able to run spectrum analyzer in realtime!

Also find out my Motu M4 has a loopback function also. But not all audio interface have one. So if not adding extra external fx then, loopback function works really well, just select enable and select loopback on input. The issue though is that the loopback causes echo from not being able to mute the loopback monitor. So reamping is best solution unless your interface can seperate or mute the loopback monitor while recording