This might have passed you by, but back in 2014, Sega commissioned a stage play to commemorate Phantasy Star Online's 15th Anniversary. Series producer Satoshi Sakai and series director Yuya Kimura supervised the play, which was produced by Masahiro Nakayama. The stage play had a short run between December 4-7 in 2014 at the Aoyama Theater in Japan, and was later released on DVD.
As part of the live performance, some musical numbers were also included. Haruko Momoi composed and wrote the songs, and these were performed by Shota Aoi and Nitta Megumi, who played the main characters Takuya and Yumi.
Takuya
Yumi
One such glorious example is provided below, the wonderfully titled "Dreamcasting." Enjoy.