Mathew Knowles grew up in a small town in Alabama and was so poor he felt he couldn't invite his friends to visit. His family used an outhouse and the side yard was littered with old batteries and refrigerators and cars. "I used to be so embarrassed about that," Knowles told Berklee students during a lecture last month.But the lessons he learned from watching his parents cope with poverty helped turn him into one of the music industry's most successful businessmen. His father earned $25 per week driving a produce truck but used that same vehicle to operate a busy junk business during his off hours. And when his mother was finished working as a maid and nanny in the daytime, she knitted quilts and sold them for additional income."I learned this entrepreneurial spirit. I learned about marketing," said Knowles, who manages Destiny's Child and several other top-selling pop artists. He also developed a philosophy rooted in his childhood experiences that applies perfectly to the state of the music business today, and decided to make it the subject of his talk: "Tough Times Don't Last, Tough People Do."Brought to Berklee's David Friend Recital Hall as this year's speaker in the James G. Zafris, Jr., Distinguished Lecture Series for Music Business/Management, Knowles also spoke as a centerpiece event in Berklee's Black History Month Music Celebration, which also featured Henry Louis Gates, Jr., and vocal group Take Six...