One song, four versions, and it still works as a release. Shirogane no Soleil's preorder disc is built entirely around "瑠璃の旋律" (Ruri no Senritsu) and honestly the melody is strong enough to carry it. The full vocal version has that mid-2000s eroge opening energy, bright synths and a female vocal lead that hits right in the nostalgia center.
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The instrumental strips it back and lets you hear how the arrangement actually breathes without the voice. The off-vocal sitting somewhere between. Five tracks total including a web radio bonus that's a fun time capsule of 2008 PC visual novel culture.
If you collect VN vocal singles, this is a clean little addition to the shelf.