It has been suggested that traversing the male (secondo) passaggio requires two important adjustments. When singing up the scale, first of all, the second harmonic (H2) needs to pass over the first formant (F1). After that, the timbre of the voice takes on a different, slightly “darker” quality. This is the pitch where, in singers' jargon, the voice reaches secondo passaggio. Above secondo passaggio, in the optimal arrangement, the second formant (F2) is tuned close to one of the higher harmonics, or, sometimes alternatively, the singer's formant cluster induces a dominant resonance in the approximate range of 2.4–3.4 kHz.