When you’re not used to processing sound and figuring out what is happening, translating that into the more familiar visual domain can be useful. You see the sharp points on a sawtooth wave, and realize that’s why it’s buzzy. Then you close the filter and watch the sharp points get rounded out and hear the buzzyness fade. In my experience, after I got better at mentally processing sound I started to want spectrum analysis more than a scope, because my brain was able to do a lot of what the scope was doing for me earlier - but I was still missing the birds-eye view of a spectrum analyzer.