Warren's years with Take 6 were characterized by a flurry of appearances, performances, recordings, and travel. Take 6 performed many concerts and embarked upon several concert tours, typically to sold-out audiences, both in the United States and abroad. In 1988, Take 6 toured approximately 12 U.S. cities, opening for singer Andy Williams. In 1989, Take 6 toured 40 U.S. cities, opening for jazz legend Al Jarreau. In subsequent years, Take 6 headlined their own concerts and tours throughout the United States, the UK, Europe, and Japan. Take 6 also performed at a number of well-known events, venues, and jazz festivals, including Radio City Music Hall, Carnegie Hall, The Hollywood Bowl, The Special Olympics, The Monterey Jazz Festival, and The Playboy Jazz Festival. Occasionally Take 6 shared billing with other, popular contemporary-Christian recording artists, such as BeBe & CeCe Winans, the Winans, and Commissioned. The popularity of Take 6 led to collaborations with many, established artists. In fact, it was through Take 6 that Warren first met Quincy Jones, establishing a musical friendship that would last for decades. Take 6 performed on several songs and interludes on Jones' album "Back on the Block." In addition to performing with the group and contributing to their vocal arrangements, Warren is the featured voice on "Setembro (Brazilian Wedding Song)", and he penned the lyrics for "The Verb To Be (Introduction to Wee B. Dooinit)". Jones also invited Warren to be a featured vocalist on the song "The Secret Garden (Sweet Seduction Suite)." At the time, for personal reasons, Warren respectfully declined the invitation. Since then, Warren has characterized it as "one of the very few decisions in my life that I truly regret." In the years since, Warren has arranged, produced, or co-produced numerous songs for various Jones projects. In 1989, Take 6 recorded the song "Don't Shoot Me," for the Spike Lee film "Do the Right Thing." Warren produced the recording and co-wrote "Don't Shoot Me" with Lee and with group-members Claude V. McKnight, III and David Thomas. That same year, Take 6 recorded background vocals on the Don Henley album "The End of the Innocence". The collaboration had been requested, as a personal favor, by Jim Ed Norman, then-president of Warner Bros. Records in Nashville. Norman and Henley were longtime friends, Norman having previously produced many recordings by Henley's band The Eagles.