As is traditional for shape note singing (see also here) the singers were seated in a square, facing inward, altos across from tenors, and basses across from sopranos.
It should be noted that these are field recordings. The purpose of the recording session was to capture the singing without interfering with the process. In particular, it was impossible to close all doors, so there is some wind sound in one of the tracks. Also, photos were taken during the singing, and so some camera noise is also present.
In the end the tracks were recorded using a stereo recording technique which uses coincident figure-of-eight microphones, oriented 90 degrees off-axis from each other. The technique, called the Blumlein Pair (see also here) after its inventor, gives a very accurate stereo reproduction of the sound at a certain point in the room. (Read more about stereo recording on this site.)
The front side of a Blumlein pair is usually positioned to face the sound source. (Picture the microphones sitting out in the audience during a concert, facing forwards towards a stage.) In this case, however, the singers were arranged in a square arrangement facing each other, and so consequently there was no "audience" and no "stage". A pair set up anywhere outside the square would be pointing at many singers' backs.
On the advice of rec.audio.pro I decided to try hanging a pair of AKG-414 B-ULS microphones from the ceiling in the exact centre of the square. Because a leader stands in the square during each song, I had to suspend the mics seven feet above the ground. The Blumlein pair worked fantastically in the centre of a group of singers.
The signal from the Blumlein pair was passed through a Drawmer 1960 acting as a pre-amplifier. The 100Hz high-pass filter was enabled, but the 1960's compression was dialled out. From the 1960 the signal was sampled by a Macintosh G4 (44.1KHz, 16bit, stereo) and saved using ProTools Free.
I was a bit nervous about the hang of the microphones... they're valuable, and I needed to hang them with their capsules touching to get coincident results. Since I couldn't use stands, the bottom microphone had to be hung from the upper one. My worst nightmare was that one of the mics would fall. In the end, I sewed the microphones together using fishing line threaded under the black housings of the mics. In the photo of the mic junction below, you can clearly see the fishing line looping around the upper mic's casing. The mics were prevented from vibrating against each other with a small loop of gaffer's tape between their housings.
To calm my nerves, I also twisted a length of 14 gauge picture wire around the two microphones, guiding it up the side of the lower mic, then bending it in along the top surface to its midpoint. From there I bent it out from the mic to trace along the housing of the upper microphone. In this way, the mics were completely supported by the wire, but no surface crossed the sensitive lobes of the capsule. The fishing-line/wire combination proved to be very sturdy, but getting it right took a few hours of picky work, and tuning it so the mics were at exactly 90 degrees to each other was a bit frustrating. The results were worth it, though!
Of course, this isn't the only way to record sacred harp music. Dan Richardson also has a very comprehensive page detailing his method for recording sings.
One note of caution: this method worked well for me, but I don't guarantee this is the best or safest way to suspend these microphones. I'm sharing my own experience here, but you should make your own assessment.
One other note, which I'm adding quite some time after the recording was made: A cut from the recording was played back on CBC Radio One, which broadcasts in mono. The mono playback of the raw blumlein pair output wasn't ideal... I'm sure this is because of cancellation between the left and right signals. Next time I'll more carefully process the output for M+S playback.
I owe special thanks to Ty Ford, JnyVee and others from rec.audio.pro for their suggestions and assistance, and to John Henderson and Pippa Hall for letting me invade their singing.