"Clear vocals" refers to a type of singing where the words sung are easy to understand. It means the singer's voice is distinct and not muffled or blurry, making it easier for listeners to hear and comprehend the lyrics of a song. Full definition
I tried playing a song with clear vocals so that I could judge the quality of the sound and - for a smartphone - this is top notch. (ubergizmo.com)
There's actually some bass in the system which reduces overall distortion and allows for clear vocals alongside bass tones. (digitaltrends.com)
When I played Carly Rae Jepsen's «Run Away with Me» on the hybrid, I noted the machine produced clear vocals and accurate synthesizer notes, and that the song's bass sounded strong. (laptopmag.com)