Question: Who's the lead singer of the doobie brothers?
Disambiguated questions and answers: question: Who's the original lead singer of the doobie brothers?
Who replaced the original lead singer of the doobie brothers?
Who became the lead singer of the doobie brothers again in 1987?
answer: Tom Johnston
Michael McDonald
Tom Johnston
Natural Questions answer: Tom Johnston (from the Wikipedia article "The Doobie Brothers")