In the late '80s, Ys I & II were two of the very first games to fully take advantage of the PC-Engine's CD add-on to deliver Redbook-audio quality music, as opposed to the typical beeps and squawks of the time. Masterfully arranged by Ryo Yonemitsu, it was really good music. A lot of the music for Ys I & II was composed by the legendary musician Yuzo Koshiro alongside Mieko Ishikawa, which greatly influenced the soundtracks of the sequels. Some notable examples:
From Ys I, we have the original boss music, Holders Of Power (in this instance set to footage from the Ys OVA).
The very first piece of Ys music - Feena (Original) and the Perfect Collection version, (which the guys who translated the Eternal games used as a replacement for the not-quite as good Eternal soundtrack version).
The opening song of Ys Origin, Genesis ~ Beyond the Beginning is, as so common in the series, awesome. And the title shouts back to the very start of the intro movie from the PC Engine Ys I, which said, simply, "In the Beginning". But of course, it takes its crown from its use in-game, before Toal Fact fights the last bosses.