Task: Question Answering
Input (English): Passage: Lukather is the original lead guitarist for Toto, serving in that capacity for the band's entire history, as well as a lead and backing vocalist and composer. Lukather won three of his five Grammy Awards for work with Toto, twice as an artist and once as a producer. David Paich led the band's songwriting efforts during the development of 1978's Toto—he penned all but two of the album's tracks, including all four of its singles. Lukather also credits Jeff Porcaro for his leadership within the band during that period. However, Lukather's role in Toto evolved over time owing to the changing needs of the band. In August 1992, Jeff Porcaro collapsed while doing yard work at home and subsequently died of heart failure. The death profoundly affected Toto and Lukather in particular, who felt that he needed to step up and make sure the band kept going. Thus, he began taking more of a leadership role.
Toto went through several lead vocalists over the years, including Bobby Kimball, Fergie Frederiksen, and Joseph Williams. After the 1990 dismissal of their fourth vocalist, Jean-Michel Byron, Toto was without a lead singer until around 1997; Lukather assumed most of the vocal duties for the band during that time. He performed lead vocals for every track on 1992's Kingdom of Desire and 1995's Tambu except for two instrumental tracks. The Tambu single "I Will Remember", co-written by Lukather and Stan Lynch, reached number 64 on UK charts. Some Tambu reviewers contrasted Lukather's vocals with those of former singers Kimball and Williams (and indeed, heavily criticized the entire album), some concert reviewers noted that he struggled vocally on certain songs, and a number of backup singers and guest vocalists accompanied the band's live shows during that period. It was not until Toto brought back Williams and Kimball to collaborate on 1998's Toto XX that Lukather returned predominantly to the role of backup vocalist.Lukather's songwriting contributions grew from a smattering of tracks on early Toto albums to co-writing almost every track starting in the late 1980s. Lukather admitted that the reason why he has no songwriting contributions on the first two Toto albums was that he wasn't writing many songs at the time, because he was intimidated by the talent of the band's chief songwriter, David Paich. He credits Paich himself with encouraging him to contribute more songs to the band. He wrote very few of Toto's songs by himself, an exception being the hit single "I Won't Hold You Back" from Toto IV. Lukather has said that writing lyrics is not one of his strengths. Thus, he collaborated with other band members to complete song ideas and make them into viable album tracks. Lukather's official site claims he contributed to writing all of the songs on Toto's 2006 album Falling in Between, even though "Spiritual Man" officially credits Paich as the sole writer. 
Question: What is the full name of the person who is the chief songwriter for the band that dismissed their fourth vocalist in 1990?
Output (English): David Paich.