What a second voice is
A second voice is a second melody, sung or played together with the main one at a different pitch. It has the same rhythm, or nearly, and follows the shape of the first voice, but it does not sing the same notes: it forms intervals with it that sound good together. It is the voice a duo sings over the melody, the one a choir puts underneath and the second guitar soloing alongside.
A good second voice hardly stands out on its own: the music gets fuller when the two sound together. That is why whoever sings the second voice needs to know the melody well and listen to the other person all the time.
Thirds and sixths, and why they sound good
Almost every popular second voice is made of thirds and sixths. The third above is the note of the key two steps above the melody; the sixth below is that same note, an octave lower. The count always stays within the key, so the third comes out major (4 semitones) or minor (3 semitones) depending on the degree. In C major, it is major above C, F, and G and minor above D, E, A, and B.
Thirds and sixths are imperfect consonances: they sound stable and sweet but do not merge into a single note the way octaves and fifths do. The frequencies of the two notes are close to simple ratios (5:4 for a major third, 6:5 for a minor third, 5:3 for a major sixth, 8:5 for a minor sixth), yet each voice is still heard as a melody of its own. That balance is what makes a duo sound together without becoming a single voice.
Example: the C major scale in thirds
Each row is a degree of the C major scale: the melody note, the second-voice note and the interval between them.
| Degree | 1st voice (melody) | 2nd voice: third above | Interval |
|---|---|---|---|
| I | C | E | major third |
| II | D | F | minor third |
| III | E | G | minor third |
| IV | F | A | major third |
| V | G | B | major third |
| VI | A | C | minor third |
| VII | B | D | minor third |
How to find the second voice
From the scale: work out the key of the song and, for each melody note, count two notes up the scale. In C major, E goes above C, F above D, and so on. Counting within the scale, the third is already major or minor in the right places. If the melody uses a note outside the key, adjust the second voice by ear.
By ear: start with the long notes and the ends of phrases. Sing the melody, hold the last note and look, a little higher, for the note that sounds with it without clashing. Many melodies end on the tonic, and the third above the tonic (C–E in C major) is a good starting point. Then fill in the rest of the phrase following the shape of the melody.
Listen before you sing: in the tool, the second voice shows up on the staff and the keyboard, and you can play both voices, only the melody or only the second voice. Hearing your part alone a few times helps you not get pulled along by the melody when you sing together.
Country duos and choirs
In a Brazilian country duo (sertanejo), the second voice usually sings thirds above the melody. When the third would get too high, the voice drops to the sixth below and comes back to the third as soon as it can. The switch works best after a rest or a long note, and the fewer switches, the more natural it sounds.
In a two-part choir, the second voice usually sits below and has more freedom: it mixes thirds and sixths, sometimes a fifth or an octave, and moves a lot in contrary motion (when the melody goes up, it goes down). At the ends of phrases, the leading note rises to the tonic (B to C in C major), and the ending usually lands on the tonic.
Common mistakes
- Parallel fifths and octaves: when the two voices move together in perfect fifths (such as C–G followed by D–A) or in octaves, they merge and sound like one thicker voice. Choirs avoid it; in thirds and sixths it does not happen.
- Voice crossing: the second voice, which was below, goes above the melody (or the other way round), and the listener loses track of the melody. If the second voice is about to cross, change octave or interval.
- A third outside the key: always singing the same distance (4 semitones) leads out of the scale. In C major, a major third above D would be F♯, which is not in the key; the right second voice is F, a minor third.
- Following the melody: without noticing, whoever sings the second voice ends up singing the melody in unison. Practising with the melody playing, and with headphones, helps you hold your part.
- Forcing high notes: if the third above climbs too high for your voice, do not force it: switch to the sixth below or change the key so both voices fit.
How to practise with the tool
The second-voice tool does the maths and plays both voices; the practice is up to you. A path that works:
- Choose the melody: one from the library, typed or sung into the microphone. Start with one you know by heart.
- Choose the style: start with “Third above”; if it gets too high, switch to “Sixth below” or “Country duo (sertanejo)”.
- Listen to both voices with “Play both voices”, then turn off the melody to hear only your part.
- Find a comfortable key with “Find the key for both voices”, which transposes the song so both voices fit the chosen ranges.
- Practise with headphones: in “Start practising”, the app plays the melody while you sing the second voice; each note lights up green, yellow or red, and you get a score from 0 to 100 at the end.
- Raise the difficulty step by step, from “Easy (±50 cents)” to “Hard (±20)”, then swap roles: sing the melody with the second voice playing.