There was no official explanation offered for exactly why Silvana Estrada and CécileMcLorinSalvant were co-headlining a show at Walt Disney Concert Hall — and none was needed, for discerning L.A. audiences who know better than to look a gift horse in the mouth. These two have little in common, representing such different cultures, styles and even languages… and everything in common, too, being among the greatest vocalists of their generations. So, why ask ¿por qué? The idea of pairing them certainly could have been generated by the LA Phil organization, which has fruitfully hosted both performers on their own before. It could have come from one artist’s camp or the other, given the mutual admiration society they obviously share. Whoever thought to match them up, the magic of McLorin Salvant and Estrada coming together made for a throughly delightful “only in L.A.” moment. (Even if it’s theoretically possible that someone in New York would have been smart enough to book it.)