In an 1988
essay published by The Journal of the Acoustical Society of America titled "Intonation precision of choir singers," results from "two experimental investigations on the acoustics of choirs" are revealed. "
The second investigation," the essay reads, "concerns the effect
of spectral variations in the reference sound."
Put super simply, the study investigated the way a choir's agreement on things like vowel formation impacted how often that choir sang at a desirable, unified frequency. Changes in vowel
quality, it said, "and absence/presence of certain partials and of vibrato,
were all found to affect somewhat the degree of fundamental frequency agreement between singers." Deviation between singers in the studied live rehearsals ranged from "
0.10 and 0.15 semitones, or 0.6% and 0.9%."
The science and mystery of aligned vowels and semitones was on full display at the Secret Sisters concert last night. And the thing is, with the way those shared-DNA harmonies washed over the room last night, you'd bet the two were nearly vocally identical. As listeners will attest, though, the two voices are quite different. Lydia Rogers' is warm and smoky with a thrilling upper register. Laura Rogers' is pure, crystalline, theatrical.
The night was all wide fifths and aching minor thirds the likes of which would have made the Everly Brothers proud, paired with softshoe melodies that wielded dark bits and daggers. Laura's and Lydia's are two acoustically sympathetic voices, voices that vibrate on the same frequency, filling in the gaps between resonances over the course of big, arching phrases, their breaths occurring in startlingly precise unison. They wove through murder ballads, a scant few covers ("Make the World Go Away") and odes to an unnamed but specific ex-lover. With their sharp rhythm section (a pair of siblings as well, Cheyenne and Will Medders), the Rogers sisters seemed on a mission to prove that a recent lawsuit and dip into bankruptcy are not only in the rearview mirror (See their 2017 release's title track "You Don't Own Me Anymore"), but that the downturn emboldened them to self-realize through their music — to cement their own identities as well as their stage personas. Or are those one and the same?