Like a majority of repliers, my first exposure was "The Wizard of Oz" because of the annual Easter airings on TV, and my mother's annual insistence that the two of us sit in front of our TV and watch the annual Easter airing. In truth, my mother and I would almost certainly continue this ritual if it were still only aired on Easter Sunday.
I was struck by this statement by Dr. Ament, "Never satisfied to be just a pretty face with a magnificent voice, Garland demonstrates how she can be on stage with anyone and make it almost impossible to watch anyone else, even though she is generous with her co-stars.".
All these years of Judy Garland film watching, and I never once considered her generosity yet it was there in every film and every dance and every duet. I don't think I'll ever view my favorite films again without watching for this graciousness.
"The Harvey Girls" isn't one of her later later films, but it has been my favorite since circa 1984 when I was home sick from school and it aired on Channel 9 in LA (KHJ at the time, KCAL now). I rarely meet anyone who holds this film in as high esteem as I, but, I swear, what Judy Garland does with a pistol in a saloon to get her restaurant's protein back remains aspirational for me.
I didn't really answer the singing/lyric question here, but I never turn down an opportunity to talk publicly about "The Harvey Girls".