Yesterday I talked about vibrato, the technique that string players use—rocking the fingers of their left hands back and forth to create small oscillations in pitch that result in a warmer, more resonant sound. Well, singers use vibrato, too—although use isn’t exactly the right word. Vibrato happens , is more like it. String players vibrate by choice, and intentionally vary the width and speed of their vibratos. But for singers, vibrato is simply a by-product of proper breathing and tone