The lyrics by Matsumoto are fairly run-of-the-mill romantic ballad imagery: rising blue moon, blooming cosmos flowers, fragile hearts with glass apples in them. But it was always that melody. I first heard it when I saw her for MY 3rd time on the 1983 Kohaku Utagassen. It was an interesting scene to say the least: she was carried down toward the stage on a silvery crescent moon decked out in a huge black poodle wig (that appearance shows up at around the 1:30 mark of the above video). Compared to her 1981 performance of "Natsu no Tobira"（夏の扉） and her 1982's "Nobara no Etude"（野ばらのエチュード） (and for that matter, the other tunes she had sung up to that point), it was a different look and different sound. Obviously not knowing about the true origins of "Glass no Ringo" during my callow youth, I just thought it was one of the weirder aidoru tunes. The indications on J-Wiki were that even the 21-year-old Seiko had taken one look at the song and just wondered "How the heck am I gonna sing this?!"
But the song did hit the No. 1 spot within 3 weeks of its debut on the charts (her 12th straight), although for a Seiko song it didn't last too long in the Top 10 of Oricon. A few weeks later, it dropped out altogether. However, it got a second wind due to its B-side....a cuter ballad titled "Sweet Memories"....the rest of the story will continue there.
Just for comparison, you can listen to the Simon & Garfunkel classic below.