Artists and producers who don’t have formal musical training often find coming up with vocal harmonies to be a hit-or-miss proposition, and may spend a fair bit of time hunting around by ear for appropriate pitches and phrases to serve as a suitable harmony. Of course, many singers - even untrained ones - are able to improvise good harmony parts, and any arranger with basic musical skills would have no trouble finding appropriate lines, but sometimes the task falls to someone who’s not really versed in the art of harmony creation.
There are a few basic techniques that can make quicker work of coming up with harmonies. Whether it’s to present a lead sheet to a vocalist for live performance or to generate artificial harmony parts from a lead vocal recording via modern pitch manipulation software, good harmonies can usually be devised fairly easily using these guidelines.
In traditional western tonal music, the most basic vocal harmony line follows the melody a musical third above the notes of the main part (unfortunately there isn’t enough room here to get into the background musical theory and terminology). Conversely, a musical sixth below the main melody will result in the same pitches an octave lower. So it might seem at first glance that the ability of modern pitch editors to transpose at will would get the job done at the push of a button. But as musicians know, there are two types of thirds, a semitone apart from each other, and to properly stay in the correct key for the song a standard third harmony typically must alternate between them. Fortunately, most pitch editors (and auto-tuning plug-ins) also provide the option to constrain transposition to notes within the current key, and this may succeed in creating a musically correct harmony line.
But sometimes harmony lines are required to jump around a little more than the main melody they’re following, in order to maintain musically appropriate pitches throughout. This is one of the classic issues when it comes to vocal harmonies - the need to maintain the song’s key can sometimes result in a harmony line that’s so jumpy that it doesn’t really hold together as a melody on its own. Such a jumpy line may sound fine under the melody, within the arrangement, but if the harmony will need to be performed - either for the recording session or later in concert - then it may prove awkward for the singer.
Harmony lines can be required to jump around a little more than the main melody they’re following, in order to maintain musically appropriate pitches throughout.
They might have difficulty rendering it in tune with appropriate musical feeling, especially if the jumps are fairly wide. This is one of the tricks of creating good vocal harmonies - it can be a little more work, but trying to come up with individual harmony lines that are comfortable melodies to sing in their own right can be helpful in getting the most musical results.
Pitch editor transpositions that constrain to key can produce a suitable harmony line from the main melody, but while a tight third harmony that follows the melody note-for-note can be musically appropriate at times, more commonly harmony parts are a bit more selective - some notes may be harmonized, while others are not, making the harmonies more gratifying when they do occur.
Harmonizing just the high points of a phrase, or the most significant words in a particular lyric can be a good way to accent those aspects of the vocal line, and this is a very common technique. The same is true with individual lines and phrases - often only certain lines of an overall vocal part will be harmonized, and the harmonies may be withheld until later in the song, so their entrance on a second or third repetition of a verse or chorus line will be that much more dramatic, building the musical intensity of the vocal part.
While single harmony lines or phrases are commonly added, many artists employ thicker, richer three or four-part harmonies. Acts that specialize in this will usually come up with their own harmonies, but a producer may want to emulate this musical approach, and will have to devise the harmonies on his own. The basis of a three or four-part harmony is still a third above (or sixth below), and the additional parts flesh out the song’s chords. A musical fifth above (or a fourth below) is added - fifth and fourth harmonies on their own tend to sound modal - like Gregorian Chant - but as part of a multi-part harmony they’ll fill out the chord. And of course octaves (and unisons) can be employed to add richness.
In fact, while doubling may not be considered a harmony, technically it’s a unison, and it can be incorporated into harmony lines to good effect. For example, the second time a musical line comes around in a song a harmony might be added, to build intensity. For an even more gradual approach to this, that harmony line could start out as a simple doubling - a unison - and then deviate from the main melody on key words or phrases at key points in the main melody.
The vocal part is subtly enhanced initially by the unison, and then more dramatically when the backing part shifts into full harmony. Octave doublings, likewise may not strictly be thought of as harmonies, but they can add a distinct edge to a vocal part, if used judiciously - the inevitable difference in tone (even if it’s the same singer) will add another dimension to the vocal part.
Just as shifting from a doubled line to a full harmony can be a musically effective gesture, vocal pedal tones can be employed similarly. Musically, a pedal tone is a steady, unchanging pitch that holds while chords change around it. The effect is distinctive, and can be quite interesting, especially if after holding a steady harmony note for part of a phrase, the backing vocal breaks into a third harmony and begins to follow the main melody at a musically dramatic point in the phrase. Needless to say, the note of the pedal tone must be one that works against all the notes in the melody that it must blend with - a unison/octave or fifth might be a better candidate than a third or sixth.
A pedal that gives way to a harmony :
In the above example, a pedal tone can hold even under passing tones - these are transitional notes in the main melody that wouldn’t be part of a standard three or four-note chord. They’ll clash a little with a pedal tone, adding a touch of dissonance - edge - but that can work to your advantage: when the phrase breaks into traditional sweet harmony, it’ll be all the more satisfying. In general, though, with a standard third harmony, passing tones might not be harmonized - the harmony line may hold the previous note or drop out momentarily. If they are harmonized, it might clash with the underlying musical (chordal) accompaniment, or just sound too mechanically slaved to the main melody, though in some cases that kind of really tight harmony can work, depending on the song and style of the music.
There are a few things to watch out for when coming up with harmonies. If the part is intended to be performed by a singer, then you have to keep the vocal range of the singer in mind. It’s easy enough to plunk out a harmony part on the piano ahead of time, but many melodies are already placed up near the top of the singer’s range (for greater vocal intensity) and harmony lines that are around a third above, and may range up to a fifth or sixth above may be out of range for the designated singer. If you’re working out parts to hand to someone (as opposed to letting the singer devise or improvise the harmonies, always another option), finding out the limits of their range in advance is a wise precaution.
If the harmonies are being created with pitch-shifting software, you’ll want to be on the lookout for the tonal artifacts of transposition. Most pitch editors are pretty good at this nowadays, but even so, larger pitch shifts can still take on an artificial quality at least to some degree - the well-known “Chipmunk Effect”. Nine times out of ten this will go unnoticed in a harmony part, since it’s slightly buried under the lead vocal, and slight tonal variations can help distinguish it from the same voice singing the main melody. But if it does sound off, shifting Formants to compensate on the notes that are the worst offenders may do the trick. That said, sometimes Formant-shifting to deliberately alter the tone can help to somewhat alleviate the same-ness of the tone - again, as long as the harmony stays suitably beneath the main vocal, this will most likely sound fine.
The art of creating vocal harmonies can be both simple and complicated - the best harmony parts are often the simplest musically, but the process of coming up with the ideal pitches and places to selectively apply harmonies for the most dramatic musical effect can involve quite a bit more thought and effort. Still, when it all comes together, there’s nothing like a nice rich harmony to enhance the vocals, in any musical style.