"Does the music correspond to the readings?"

I had the pleasure of hosting several college students the other night who had expressed interest in learning and singing sacred music. At one point, I gently explained that instead of the usual pick-a-song approach, the Church actually prescribes preferred music in the Graduale Romanum…

…at which point a young lady eagerly asked if this music corresponds to the readings. "I like it when it does that," she told me. Not wanting to deflate her enthusiasm, I smiled and said that yes, it often does — even though I knew better. I think.

Am I correct in understanding that the whole notion of readings corresponding to one another (first reading, second reading, Gospel), let alone the music corresponding to the readings, is a fairly recent phenomenon? For the Liturgy of the Word, I understand that although there may sometimes be some thematic connection (particularly between the Epistle and the Gospel), the readings are often fairly independent of one another.

And for the music, would I have been correct in explaining to her (again, gently) that the Propers are actually sung Scripture ("readings") in and of themselves, and that as such, each Proper stands alone as part of the whole of the Mass… that the music here isn't really meant to serve in a supportive role to the spoken readings?