There were a few vinyl records made in the 1970's by Lincoln Mayorga that were direct-to-disc to enhance the dynamic range and recording accuracy of the instruments.

We always used these in my shop back then to demo Audio Research and Magnepan systems, which were the best in those days.  We also recorded them onto a Nakamichi 1000 and played it through the same system to hear the differences between the original vinyl and the cassette tape (Their Dragon was a later invention.)

As for regular vinyl, we used Maria Muldaur's "Midnight at the Oasis" song and, as it was VERY POPULAR with the younger set, Pink Floyd's "Money" as well.  Customers really liked that one, although I was not that impressed with the recording.  The fabulous singer Linda Ronstadt was also a good choice.  Back then, female voices were used as a kind of benchmark for listening.

Orchestral sounds were mainly London Decca vinyl versions of whatever we had on hand.  Customers usually brought their own stuff if they were serious about wanting to listen to different set-ups. 

A local competitor/dealer, Peter McGrath, used a Stellavox and some good microphones and went around recording live music that he used in his shop in Coral Gables.  He became a bit famous for the quality of his recordings for a while, and they were pretty good!

As for digital, it was not invented yet and today, when I listen to my CD's, I am always going back to vinyl for what I believe is more accurate playbacks.  I guess it depends on what you are used to.

Cheers!
Simply listen to things you're familiar with that have at least a modicum of dynamics, and remember to work the word "modicum" into statements as people will think, "Hey, that guy's real smart."
One song I always use is "it's oh so quiet" by Bjork, i think its on her Post record.  
I always come back to -
Rickie Lee Jones "S/T" and her other stuff. "Pop" is fine. No speaker or system has still managed the screaming baby perfectly.

Listening now to Richard Bona track Djombwe & I Wish & Trains. Very live. Not bad at all....

Some of these recommendations are new to me. Will try them.