"Parasite Eve" was the first of her projects to include a vocal theme, the ending theme "Somnia Memorias". This was because the PlayStation system was the first to have sufficient processing power for this to be possible. For the vocalist, Shimomura avoided using someone well known. "Somnia Memorias" was sung by Shani Rigsbee, while the vocals for the orchestrated versions of "Influence of Deep" and "Se il Mio Amore Sta Vincino" were provided by Judith Siirila. "Somnia Memorias" was translated and adapted from Japanese into Latin by Raul Ferrando, while "Se il Mio Amore Sta Vincino" was translated by Daniella Spagnolo. The lyrics for all vocal pieces were written by Shimomura. The track "I Hear a Voice Asking Me to Awaken" was an arrangement of "Wachet auf, ruft uns die Stimme", BWV 140 by Johann Sebastian Bach.