Sunday at 1 p.m., WRTI-FM (90.1) presents a March concert by the Philadelphia Orchestra under conductor Alain Altinoglu, and featuring organist Michael Stairs. Gabriel Fauré's intimate and contemplative Requiem is the centerpiece of a spiritual program that also features Gabrieli's "Canzon septimi toni, No. 2," from Sacrae symphoniae, Franck's Organ Chorale No. 1 in E major, Villa-Lobos' Bachianas brasileiras No. 5, Duruflé's Four Motets on Gregorian Themes, and Paul Dukas' Fanfare From La Péri.