Rap never seems to grow stale. Instead it mutates, throwing off fresh new shoots. I won't apologize to its enemies (who never saw anything in it but violence), but the latest offshoot might be described as quieter rap. De La Soul, which was one of the genre's sensations last year, showed how friendly and relaxed this new style can be. Now we have A Tribe Called Quest, four young guys from Brooklyn and Queens who are tender enough to begin their debut album, People's Instinctive Travels and the Paths of Rhythmwith the sound of a baby crying. They don't brag and don't fight; they hardly even raise their voices.
The music they put behind their rapping doesn't raise its voice either. It has a casual sound, something like laid-back jazz, but more likely to surprise you with, say, a touch of mariachi or flamenco guitar.
The band members talk as increasing numbers of black people do about what they call their Afrocentric way of living. Just when you're wondering why they don't define what that is, you realize they've done something better: With no fuss at all, they've more or less exemplified it. They call themselves a ''tribe'' and proceed, consciously or not, to act tribally. They surround themselves with friends, bouncing phrases back and forth in a way that sounds like both American conversation and the traditional African pattern of call and response.
Their best-known single so far is a piece of teenage fluff called ''I Left My Wallet in El Segundo,'' about an aimless drive from Brooklyn out west and back, after which they have to head west once more because hey, check out the title.
Other songs can be harder to figure out, because the words themselves take unexpected trips. ''Afrocentric living is a big shrug,'' the Tribe says in ''Can I Kick It?'' ''A life filled with music, that's what I love/A lower plateau is what we're above.'' But they don't say ''music.'' Instead, where that word would come, they insert a quick, happy musical outburst. Quieter rap turns out to be more complicated rap as well. This Tribe won't hit you on the head with its quest. But you'll be rewarded if you listen to it closely. A-