Strictly speaking the Hymn Crystals are items similar to the Grathnode Crystals, but unlike them, they don't have any special qualities, and no matter how much energy or from which direction that energy comes, they can't be interfered. If one of these crystals was Installed in a Reyvateil, the wave interferences would cancel each other, and it wouldn't affect the Static H-Waves of the Reyvateil at all (in short, they have a GD (Grathnode Damage) Value of 0), which makes Installing them pointless.