Because the studio song is playing and him yelling the lyrics is slightly more quiet. Until he jams with no music where he's using a thing called pitch tuner where it makes you sound good but not sound like auto tune. It tunes one's pitch.
Baby, I need you in my life, in my life Please, bae, don't go switching side, switching sides I swear this is where you reside, you reside Please bae, don't go switching sides, switching sides Yeah, yeah, yeah, yeah Ooh-ooh, please don't throw your love away, huh Please don't throw your love away, huh Please don't throw your love away, huh Yeah, yeah, yeah, ay
