- Opferleid by Zelter, Karl Friedrich
- Opferlied by Beethoven, Ludwig van
- Opferlied by Beethoven, Ludwig van
- Or che il ciel a me ti rende by Mozart, Wolfgang Amadeus
- Or che il ciel a me ti rende by Mozart, Wolfgang Amadeus
- Or che il ciel a me ti rende by Gamerra, Giovanni de
- Or che il cielo a me ti rende by Righini, Vincenzo
- Or che le rèdole by Donaudy, Alberto
- Or che le rèdole by Donaudy, Stefano
- Or che siete speranze tradite by Stampiglia, Silvio
- Or che siete speranze tradite by Händel, Georg Friedrich
- Or la tromba by Rossi, Giacomo
- Or la tromba by Händel, Georg Friedrich
- Or sai chi l’onore by da Ponte, Lorenzo
- Or sai chi l’onore by Mozart, Wolfgang Amadeus
- Or son sola alfin respiro by Auber, Daniel
- Or son sola alfin respiro by Scribe, Eugène
- Or sono sei mesi by Civinini, Guelfo
- Or sono sei mesi by Puccini, Giacomo
- Or sono sei mesi by Zangarini, Carlo
- Ora e per sempre addio by Boito, Arrigo
- Ora e per sempre addio by Verdi, Giuseppe
- Oración de las madres by Bautista, Julián
- Oración de las madres by Falla, Manuel de
- Oración de las madres by Martínez Sierra, Gregorio
- Oraison dominacale by Caplet, André
- Oraison dominicale by Gourmont, Remy de
- Oratorio de Noël
- Oratorio per Santa Francesca Romana
- Orazio Cocle
- Ordinary
- Ore dolci e divine by Puccini, Giacomo
- Ore dolci e divine by Adami, Giuseppe
-
Orfeo ed Euridice
- Che disse! ch’ascoltai… Addio, addio, o miei sospiri by Gluck, Christoph Willibald
- Che farò senza Euridice by Gluck, Christoph Willibald
- Che fiero momento by Gluck, Christoph Willibald
- Che puro ciel by Gluck, Christoph Willibald
- Chiamo il mio ben cosi by Gluck, Christoph Willibald
- Deh placatevi con me by Gluck, Christoph Willibald
- Gli sguardi trattieni by Gluck, Christoph Willibald
- Orff, Carl
- Orlandini, Giuseppe Maria
-
Orlando
- Amor è qual vento by Händel, Georg Friedrich
- Chi possessore è del mio core by Händel, Georg Friedrich
- Così giusta è questa speme by Händel, Georg Friedrich
- Lascia Amor e segui Marte by Händel, Georg Friedrich
- Non potrà dirmi ingrata by Händel, Georg Friedrich
- Quando spieghi by Händel, Georg Friedrich
- Sorge infausta by Händel, Georg Friedrich
- Tra caligini profonde by Händel, Georg Friedrich
- Verdi piante, erbette liete by Händel, Georg Friedrich
- Orlando finto pazzo
- Orlando furioso
- Orphée 1 by Apollinaire, Guillaume
- Orphée 1 by Durey, Louis
- Orphée 1 by Ballif, Claude
- Orphée 2 by Apollinaire, Guillaume
- Orphée 2 by Durey, Louis
- Orphée 2 by Ballif, Claude
- Orphée 3 by Apollinaire, Guillaume
- Orphée 3 by Durey, Louis
- Orphée 3 by Ballif, Claude
- Orphée 4 by Apollinaire, Guillaume
- Orphée 4 by Durey, Louis
- Orphée 4 by Ballif, Claude
- Orphée aux Enfers
- Orphée et Eurydice
- Orpheus by Blitzstein, Marc
- Orpheus by Pasatieri, Thomas
- Orpheus by Gurney, Ivor
- Orpheus by Castelnuovo-Tedesco, Mario
- Orpheus with His Lute by Bunge, Sas
- Orpheus with His Lute by Schuman, William Howard
- Orpheus with His Lute by Greene, Maurice
- Orpheus with His Lute by Sullivan, Sir Arthur
- Orpheus with His Lute by Gardner, John Linton
- Orpheus with His Lute by Quilter, Roger
- Orpheus with His Lute by German, Edward
- Orpheus with His Lute by Vaughan Williams, Ralph
- Orpheus with His Lute Made Trees by Shakespeare, William
- Orr, Charles Wilfred
- Orrida a gl’occhi miei by Anonymous Italian Poets
- Orrida a gl’occhi miei by Händel, Georg Friedrich
- Orsames’ Song by Suckling, Sir John
- Orsames’ Song by Parker, Horatio William
- Orsini, Flavio
- Ortega, Francisco
- Orthel, Léon
- Osma, Julio de
- Osterwald, Karl Wilhelm
- Otello
- Otello
- Otterström, Thorvald
- Otto, R.
- Ottoboni, Pietro
-
Ottone
- Affanni del pensier by Händel, Georg Friedrich
- Ah! Tu non sai by Händel, Georg Friedrich
- Deh! Non dir, che molle amante by Händel, Georg Friedrich
- Del minacciar del vento by Händel, Georg Friedrich
- Dove sei, dolce mia vita by Händel, Georg Friedrich
- Giunt’ in porto è la speranza by Händel, Georg Friedrich
- La speranza è giunta in porto by Händel, Georg Friedrich
- Le profonde vie dell’onde by Händel, Georg Friedrich
- Purchè regni il figlio amato by Händel, Georg Friedrich
- S’io dir potessi by Händel, Georg Friedrich
- Trema, tiranno, ancor by Händel, Georg Friedrich
- Où va la jeune Indoue by Gondinet, Edmond
- Où va la jeune Indoue by Gille, Philippe
- Ou va la jeune Indoue by Delibes, Léo
- Où voulez-vous aller by Gautier, Théophile
- Où voulez-vous aller? by Gounod, Charles
- Oudrid y Segura, Cristóbal
- Oui, des choristes du théâtre by Leuven, Adolphe de
- Oui, des choristes du théâtre by Brunswick, Léon Lévy
- Oui, des choristes du théâtre by Adam, Adolphe
- Oui, ta voix m’inspire by Royer, Alphonse
- Oui, ta voix m’inspire by Donizetti, Gaetano
- Out of the night by Korbay, Francis Alexander
- Ouvre tes yeux bleus by Massenet, Jules
- Ouvre tes yeux bleus by Robiquet, Paul
- Ouvre ton coeur by Bizet, Georges
- Ouvre ton coeur by Delâtre, Louis Michel James Lacour
- Ov’è la voce magica by Anonymous Italian Poets
- Ov’è la voce magica by Donizetti, Gaetano
