[Lazortag]

The weird thing about cessation stacking with selo's consonant chain, is that clearly both songs are working at once and no song gets entirely overwritten, since you see the mob moving slower (because it's snared) but the mob takes damage from the dot from chords of cessation. Both songs have a slow effect, and selo's consonant chain's is the more powerful one, so presumably it overwrites that of chords of cessation, but it doesn't stop the entire song from working (ie it doesn't overwrite the dot component of it). Maybe this is a bug, I dunno.

edit: as for song of highsun, I found a post from 2001 confirming it as day-only, so it probably only changes in Luclin, unfortunately.