Answer by taking a quote from the following article:

Kevin Moore (born May 26, 1967) is an American keyboardist, vocalist, composer, and founder of the Chroma Key music project. He is also a former member of the American progressive metal/rock band Dream Theater, co-founder of the progressive rock supergroup O.S.I. and has composed film soundtracks. Throughout his career, he has become known for his emotional music and lyrics, nomadic lifestyle and use of spoken word samples. Moore started his music career in progressive metal band Dream Theater.

Dream Theater's debut studio album was 1989's When Dream and Day Unite, which earned the group comparisons to well-known progressive rock bands such as Rush and Queensryche. Their big breakthrough, however, came in 1992 with the album Images and Words, featuring the band's highest charting single to date, "Pull Me Under". The song, which included lyrics by Moore, reached #10 on the Billboard Mainstream Rock Tracks chart. Following their relentless touring in support of the second album, the band also went on to release a live album, Live at the Marquee, and a video, Images and Words: Live In Tokyo. The video's extensive documentary footage would subsequently introduce many fans to Moore's ironic sense of humor.  In 1994, the band released its third studio album, Awake, which was the band's highest charting album to date with Moore, reaching #32. The album featured Moore's signature song, a haunting piano-driven ballad called "Space-Dye Vest." Shortly before the album was mixed, though, Moore announced to the rest of the band that he wished to concentrate on his own musical interests and would be quitting Dream Theater. According to Portnoy, Moore became interested in the independence of working on his own as opposed to the compromise of a band environment. Although Dream Theater has since invited him to play reunion shows, Moore has said he prefers to move forward as opposed to looking back. He also declined to take part in the official Dream Theater biography titled Lifting Shadows.  During his time in Dream Theater, Moore wrote the lyrics to songs on each of the band's albums and also to some of the band's demos and b-sides. On When Dream and Day Unite, he wrote "Light Fuse and Get Away" and "Only a Matter of Time." On Images and Words, he penned "Pull Me Under", "Surrounded", "Wait for Sleep", and parts of "Take the Time." On Awake, the songs "6:00", "Lie", and "Space-Dye Vest" all featured his lyrics. Demos with his lyrics include "Don't Look Past Me," the final verse of "To Live Forever '94," "A Vision," "Vital Star," and "Two Far."

How did When Dream and Day Unite do on the charts?
the band's highest charting single to date, "Pull Me Under". The song, which included lyrics by Moore, reached #10 on the Billboard Mainstream Rock Tracks chart.