A New World Woman
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The results aren’t as crisp as with an oscilloscope; but you can get very similar dancing curve effects with a fairly trivial mod to a standard CRT: just disconnect the electromagnets that guide the electron beams from the driver boards and run the signal of your choice through the one that handles x deflection and the one that handles y.
For extra convenience, the electromagnets on modest size CRTs are close-enough-ish to the impedance and power handling of smallish speakers that fairly typical audio amplifiers can drive them hard enough to deflect the electron beam all the way to the edge; but not so hard that anything catches fire or gets overdriven to death particularly quickly. You get neat looking, if somewhat chaotic, results from music(assuming it has some stereo separation, otherwise you just get a diagonal line whose length changes with volume); but audio amps will accept a pretty wide range of inputs without murdering the source or killing themselves; limited mostly by having little incentive to do a good job with anything north of 20khz, so all sorts of options are viable.
As noted, inferior to an oscilloscope; but has the virtue of being readily improvised out of electronic trash(especially if you start with a TV that has speakers; in which case you get the CRT and the audio amps in one package and can complete the modification by disconnecting and reconnecting a grand total of 8 connectors and drive the result through its existing RCA ins; luxury.)
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I picked up the deluxe 12-in-1 version that has Asteroids, Centipede, Tempest, and 9 other games on it. A little spendy ($400 or so) compared to a DIY or other tabletop JAMMA console with hundreds of games, but still a really fun set of games - several key horizontal ones were not available on my JAMMA unit.
Tip on the Asteroids/Tempest cabinet: the spinner is super light, and clicks. There are a couple cheap/easy mods that are fairly essential to do to make the spinner more usable. Basically, adding some filler to the (empty) plastic spinner to give it more proper weight, and wrapping the spindle in a bit of electrical tape to reduce the clicking. Others take the OEM assembly out completely and put in a “real” spinner with counterweights and whatnot, but I was lazy. 
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Thank you!
I raised a daughter who is also a Rush fan, so we graciously accept that honorific.
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Awww, happy anniversary! A perfect anniversary gift. Very thoughtful.
Also, that’s one of the best nerd stories I’ve ever heard. Made me teary.
Here’s to you both, and I wish you many more happy years together.
ps-
I’ve got a super soft spot for your story, as my husband and I “dated” at the arcade as well. Married 30 years this May.
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I didn’t think it was that easy (and the idea of using internal audio amplifier is awesome), but I’ve seen something like that in a semi-commercial product - an oscilloscope that was obviously a converted TV in a custom case. It was intended for classroom use, probably because of its huge screen and low cost. If it had X-Y mode, it could work as a vector display without any modifications.
I’d be interested to know how much massaging they had to do to get reasonably adequate oscilloscope behavior out of something born as a TV.
As noted; overriding the driver board and getting hands on control of the electron beam deflection is almost astonishingly easy; and the results are certainly reminiscent of an oscilloscope; but I’d very much doubt if such a hackjob enjoys, say, linearity in terms of how much voltage translates into how much movement across the entire range; or any sort of resistance to the electromagnets being big fat inductors and blunting your signals or any of the other fiddly concerns that real test equipment must concern itself with.
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