Betany Coffland at the Red Poppy

I used to know a vocal teacher, Maestro Salvatore d'Aura, who began his career by working for Puccini (no, really), and who had an interesting, almost mathematical theory about vocal production. The aim of beautiful (bel canto) singing is to convert breath into tone. Those who convert the highest percentage of breath into tone are the finest singers.

I was thinking about this recently when I heard mezzo Betany Coffland, whose voice is so fulsome and clear that I consider it almost magical. It was even more obvious in the cozy confines of the Red Poppy Art House in San Francisco, where she performed an evening of songs with guitarist Aaron Larget-Caplan. Following a tour of New England (where the two first met, at the New England Conservatory), they've been performing around the Bay Area.

The evening is a sublime and varied offering, beginning with Joaquin Rodrigo's dramatic, flamenco-flavored "Aranjuez, Ma Pensée" and two traditional Spanish guitar solos, Pascual Marquina's paso doble "España Cañi" and the jewel-like serenade of Albéniz's "Granada." What follows is the pairing of two songs by 17th century composer John Dowland with two songs by Benjamin Britten, who cited Dowland as an influence. The descending lines of the second Britten piece, "The Big Chariot," were a revelation.

The second half began with two luscious songs by 20th century composer Reynaldo Hahn (transposed from piano by Larget-Caplan) and a couple of modern guitar solos, including the intriguing "Ed é subito sera" by local composer Ken Ueno. Ueno's piece operates around a high drone, bringing to mind insects hovering over water.

The evening ended with Seven Popular Spanish Songs by Manuel de Falla (1876-1946), inspired by the regional folk styles of Spain. The series gave full range to Coffland's agile instrument, especially the fierce finale, "Polo," and jaunty opener, "El Paño Moruno." In addition to the musical delights, the performance was a fine demonstration of the advantage an opera singer has in lending a character and point-of-view to each piece, often through the smallest of expressions. Even listening to songs in Spanish or French, the observer could understand what was going on in the brief narrative of each work.

The pair will perform again April 27 at Willits Community Theatre and at 405 in San Francisco, 7 p.m. May 2.