Sacred: Sanctus from Charles Gunod's Mass in Honor of St. Cecilia as sung by Kiri Te Kanawa in her Ave Maria Album; Ave Maria, by Franz Schubert by numerous artists and orchestras; Gunod's Mass for St. Cecilia (in its entirety) Just as I am, buried in the Hymns Triumphant album, by the London Philharmonic Choir; Berlioz's Te Deum.
Secular: (Clasical) Humming Chorus from Madame Butterfly, but only the version by the Bavarian Radio Chorus from the CD: The Only Choral CD you'll ever need; Joshua Bell's violin version of Puccini's O Mio Babbino Caro from his Romance of the Violin CD; Any version of Claude DeBussy's Claire de Lune; the stupendous choral movement from Beethoven's Ninth Symphony; Issac Albeniz's Asturias, by John Williams in his Greatest Hits CD.
Secular: (Traditional and Country)Barbara Allen as sung by Emmy Rossum on the Songcatcher CD from the movie of the same name; Will the Circle be Unbroken, by the Nitty Gritty Dirt Band; Gonna Find Me a Bluebird, by Marvin Rainwater; Your Cheatin' Heart by Hank Williams; Young Love by Sonny James; Red River Valley; Battle Hymn of the Republic by the Mormon Tabernacle Choir.
Secular: (Pop and Rock) Goodnight Irene by the Weavers; Oh My Papa by Eddie Fisher; The Third Man theme, by Guy Lombardo, but especially the version by Anton Karas from the movie of the same name; The Wayward Wind, by Gogi Grant; The Poor People of Paris, by Les Baxter; So Rare by Jimmy Dorsey; Theme from A Summer Place by Percy Faith; I Will Follow Him by Little Peggy March; Only the Lonely and Running Scared by Roy Orbison; It Doesn't Matter Anymore by Linda Ronstadt, Please Come to Boston-- Harry Chapin or Joan Baez do a great job; El Condor Pasa, by Inkari (Music of the Andes CD) or Simon and Garfunkel; Theme from Chariots of Fire by Vangelis; Longer by Dan Fogelberg; Memory by Barbara Streisand; Untamed Heart, by Cliff Eidelman; No Matter What by Boyzone; Time to Say Goodbye by Sarah Brightman and Andrea Bocelli; Show Me How to Love You by Sarah Brightman and Jose Cura; and several songs, whose titles I don't have time to look up, by Celine Dion.
-- just a selective and subjective submission for your approval.