You can calibrate a scope with a DC voltmeter if you can make good enough square waves. I digital meter that can measure one volt with two digits after the decimal point has so much more resolution that it just doesn't matter anymore. You have to match the amplitude to the DC reference. With some generators it can be a bit tricky, plus the fact that you cannot count on it for the high frequency alignment of the scope. For that you should have an accurate detector probe to be able to measure a sine wave, even if it is not true RMS, you'll be comparing that to the trace on the scope so the meter is more accurate enough so that you can get it close enough for audio work.
Aligning a scope is like aligning the IF strip of an FM or TV set. You are already supposed to know the intended results and be able to read it from the response you measure. All the instructions do really is to point to where the controls are, and if you are clueless, then where to start.
But you really shouldn't be clueless if you are trying to align a scope. And let me tellya, when you get to those higher frequencies it turns into a real pain in the (_|_). you gotta use the friggin 50 ohm connectors n shit, ugh. And then, I was having a go at this (results were not all that bad though...) and found that someone had put friggin 75 ohm cable on BNC connectors ! I had more standing waves than waves ! OK, that is an exagerration but it made a mess. As a result I still don't have the high end of that scope aligned. It is good for general work but is supposed to be a 275 MHz. I can assure you it is not. Last guy tried a retrofit for an unobtainium vertical output IC and failed. He tried to realign the whole thing for that and pretty much rolled it. I tried a better retrofit, but then since we had another 1725a come in I decided to just install the correct part. It is close enough for now, later I'll get the detector probe and a few other things and hammer the rest of it out. Man this guy screwed with EVERYTHING. I know what he was doing, trying to get more gain. That was the problem with my retrofit, though mine was a hell of alot better. Got it from a site in Russia or something.
Good old analog scopes are the best thing going. I have had them connected to my stereo at times, and know other who like to do that as well. A scope is literally an eyeball. It is like a meter may hear, but the scope sees.
Anyway, as people have said not to tamper with like FM alignment unless you know what you're doing, this is the same but in spades.