Originally Posted by
GalaxiomAtHome
....It is done by pumping energy into the high frequency components of the other sounds in the same way a phase locked loop works in electrical signals. If you were to hear this kind of backing in isolation it would sound quite strange.
I don't quite understand what you mean here. Can you give an ( audio) example of this ?
I don't have audio examples but a couple of concepts might help.
All sounds are made of fundamental resonances and a series of harmonic overtones at higher integral multiples of that frequency.
Symetrical vibrations produce even numbered harmonics while asymetrical vibrations produce odd harmonies. These sounds are typified by the flute which resonates symetrically because it has two open ends and reed instruments such as the clarinet which vibrate asymetrically.
Guitars produce both because the string resonates both symetrically (full length) and asymetrically (from the fixed position at the bridge and nut). Singing the sound of the guitar is a very good exercise at rounding the voice.
Often backing picks up on the resonances of the lead voice and selectively reproduces the highest frequency components without masking its character at the lower frequencies. We just pump what is known as the formant which is centered around 2800Hz.
This frequency is is centred between the sixth and eighth harmonics of 400 Hz (A above middle C) which is the peak of our hearing accuity. The sixth is the product of one odd and one even resonance. The eighth is a third generation even harmonic. The ninth is the second product of an odd harmonic.
The harmonics of the entire scale converge at in this frequency range so it is of central importance in singing to develop the formant resonances. The backing singer can help produce a formant for a lead.
The high frequency components of the sound have a powerful role in tuning. Guitar players will be familiar with the beat that occurs when two strings are not quite in tune. We hear the difference between the two frequencies. The higher harmonics also produce a beat when they are out of tune but the beat is very fast so any deviation from tuning can be much more quickly detected.
Taking contol of this region of the sound has a profound effect on the tuning of the lower freqencies. The fundamentals absorb some of the the energy of the formant by allowing their own frequency to lock into a subharmonic of the formant that is pumping them. It brings the fundamental sounds not only into tune but into phase.
The same principle is used in radios and is known as Phase Locked Loop.
Another part of a backing singer's job is to balance the odd and even harmonies present in the lead and the instruments. Sometimes I find myself injecting a lot odd harmonics when singing with several others who can resonate well together. Sometimes I will sing a fairly powerful twang into a sound to give it a bit more definition.
A backing singer can put a sharp attack onto parts of the lead's voice. This triggers a burst of odd harmonics to increase definition of the words. This is particularly useful when several voices get together and the words become indistinct due to the smudging of the attack by several slighly different onsets among the voices.
Sometime I don't sing the beginning of the word at all but instead hold the note while the lead breathes.
Consequenly I often sing broken pieces of songs, distorted towards odd harmonics, with enhanced energy in the higher frequencies and sharp edges. Thats is what I mean by it potentially sounding odd in isolation.