Any recommendations on medium price oscilloscope? How do you hook it up - insert it into the 1/4" signal path? I've never used an oscilloscope so I fear I'll order something close sounding but completely wrong :)
Used Tektronix analog scopes would fit the bill, for around the same price as the Korg.
2200 series and 2400 series are probably the sweet spot in terms capability for money, weight, reliability and repairability. I particularly like the 2245 and 2445, which have basic (digital) measurement capabilities and digitally controlled attenuators. 2225 and 2215 are also solid options. I would stay away from the analog/digital hybrid and digital scopes from this series (243x, 2440, 2210, 2212, etc).
T900 series scopes are good too, but have somewhat lower specs.
400 series scopes are just as capable as the 2200/2400, but much heavier, older and more likely to need re-capping. Some 400 series also have a not-very-good built in DMM.
For audio work, you could also check out the 5000 series mainframe scopes, but that inevitably leads down the rabbit hole of wanting all the plugins (and there are many neat plugins!)
There are also a ton of new $200-class digital scopes from china.
Used Hameg scopes are common and fairly inexpensive, as they were used a lot in schools (at least in my area), and their manuals are very good for learning about oscilloscopes.
To hook up your 1/4" signal, add a splitter to your output, and use one side to drive whatever you're outputting to, and the other side to measure the signal on the oscilloscope. Ready made 1/4" to BNC adapters are available, so you don't even have to use oscilloscope probes
