Denis Kilty continues this 3 part series on capturing a choir.
Capturing The Sound
Choirs can be physically arranged in a multitude of ways for recording, each way chosen to accurately reflect both he performance capability of the singers and the level of isolation required for mixing. The most standard way is SATB in two lines, Soprano and Alto at the front with tenor and bass lined behind. This particular set up is designed for whole takes, so due to the level of spill, what is recorded is what you get. It is also possible, if the choir is of a high enough standard, to mingle the singers to create a total vocal blend at source. This requires total independent knowledge of the music and a strong sense of place within the ensemble from each member, so reserve this set up for the best of ensembles. Ensembles can also be split according to gender, with tenors and basses on the left and sopranos and altos on the right. Often choirs record in a slight semi circle, with the lines of singers “honeycombing” (looking between the shoulders of the person in front fro projection clarity). This tightens the stereo image as the singers at the edge are closer to the stereo microphones.
To record this positioning, a number of techniques can be used. An XY stereo pair of cardioid condensers placed in front of the choir is a good place to begin. The XY configuration captures a decent Stereo image and the inherent crossover between microphones creates quite a concrete center image too. An expansion of this is to instead use two Figure Of 8 patterned condensers in the same format, also known as the Blumlein Pair. This technique captures the same focused stereo image but the bi-directionality of the microphones means that the stereo room ambience behind the microphones is also captured.
Alternative microphone configurations that can work include the ORTF positioning and the Spaced Pair. The Spaced Pair is a pair of omnidirectional condensers separated by several feet (depending on the size of the ensemble.) and parallel to each other. This configuration can help capture a wider stereo recording, but the center image often suffers due to the distance between microphones. ORTF is a good alternative as the closer proximity between microphones and the 110degree outward angle helps ensure a tighter center image and a more realistic listening experience. The microphones capture variance in time and volume between the arrival of sound at the left and right microphone, helping spatialise sounds more accurately in the stereo field.
Finally the Decca Tree configuration (seee above) is a great configuration for ensembles., favored in classical recordings due to its ability to capture a wide and consistent stereo recording. Placing two microphones about 1.5 meters apart facing the left and right and a third directly at the choir, in an upside T shape, the Decca Tree is most commonly placed above the head of the conductor. This is to allow for the optimal recording distance, given that the conductor manipulates the choir to optimally perform to him, much how often the best location for a live concert is beside the live sound engineer.
The two main things to remember when placing for ensemble vocal recordings is the critical distance and phase alignment. That the higher up and further back the microphone array is, the closer to the critical distance the microphones will be. The critical distance refers to the point where the source sound crosses over to the room reflection (dry to wet). If you want a more defined sound, you need to move closer overall to the ensemble, essentially mixing the dry source signal and the wet room signal through microphone placement.
Secondly, the more stereo techniques you use, the more likely you are to run into phasing issues. Always take a moment to phase reverse one channel on each stereo pair to make sure that you are not cancelling out the stereo image for that recording. Once it is recorded out of phase…you are in trouble!
There is a lot more to say about ensemble vocal recording, but the most important points to take away are microphone placement, room appropriateness and an informed efficient rapport with the conductor. After that, anything goes!
Denis Kilty is an Irish music producer, songwriter and composer for commercial and game music, based in Dublin City. – www.deniskilty.com