Elfen Lied's opening, Lilium, is a symphony sung in Latin.
Was it written/composed just for Elfen Lied (like for example, the opening songs for Pokemon)?
The answer is yes.
According to the pamphlet included in the Elfen Lied OST, the melody of Lilium just surfaced to MOKA, the two-person musician group who was appointed the music producer staff of the Elfen Lied anime TV production team, when they looked at Elfen Lied from a certain perspective: it's not that Lucy wants to be born special — what she desires, the mundane happiness, that which appears to be easily obtainable is in fact obtainable by only a small handful of people.
As is almost always the case with anime music, Lilium was composed just for Elfen Lied. KONISHI Kayo and KONDO Yukio collectively handled the composition, arrangement, and lyricwriting (and also did the rest of the soundtrack).
Lilium was inspired by the poem 'Elfenlied' which is in the Manga, written by Eduard Mörike, and later adapted to a Lied by Hugo Wolf.
Nope I don't think so guys.. maybe the music was composed solely for Elfen lied but the words (lyrics) are taken from the bible and other catholic prayers.. Like chapters of the bible Psalms and James and a prayer of the Holy Mary.. as the peeps before me have said yes the two yukio and kayo composed it but they themselves have said they have taken the words from the places which I mentioned above..