Opera, the Italian, 141; advent of, 148; Europe addicted to the habit of, 220; opposition to, 221, 222; production of the first, 247; Scarlatti's improvements in, 265-269; the laws of, 272; new school of, 286, 287; in France, 294, 295, 312; in Germany, 337; fatal weakness of, 341. Opera houses, 262. _Opera per Musica_, the title, 252. Opera writers, Italian, 264, 265, 271. Operas, Gluck's, 222, 313; Monteverde's, 150, 259; Cavalli's, 263; Scarlatti's, 265-269; Rossi's, 271; Caldara's, 271; Lotti's, 271; Buononcini's, 271; Handel's, 272; Cimarosa's, 276; Rossini's, 277; Donizetti's, 280; Bellini's, 280, 281; Mercadante's, 281; Verdi's, 281, 282; Perrin's, 295; Lulli's, 302; Rameau's, 309; Méhul's, 322; Cherubini's, 322; Spontini's, 323; Auber's, 323; Halévy's, 323; Meyerbeer's, 324; Gounod's, 329; Bizet's, 331; Saint-Säens', 332; Massenet's, 333; Reyer's, 334; Keiser's, 339; Mozart's, 110, 140, 340; Weber's, 349; Beethoven's, 353; Marschner's, 355; Cornelius', 355; Goldmark's, 356; Wagner's, 358. Operatic declamation, 129. Operatic finale, Piccini's development of, 275. Opitz, Martin, 336. Oratorio, 48, 79; advent of, 148; origin of, 199; influence of Greek plays upon, 200; Neri's influence upon, 202, 203; effect of dramatic recitative upon, 203; first performance of, 203; improvements of Carissimi, Stradella, and Cesti in, 204, 205; dates from Handel, 207; its decadence after Handel and Bach, 220; descriptive orchestration in, 224; its popularity in England, 232; improvement in the dramatic recitative and the choral part of, 264. Oratorio, Passion, 212. Oratorio, Protestant, Mendelssohn attracted towards, 227, 230. Oratorios, Handel's, 201, 207, 313; Carissimi's, 204; Scarlatti's, 205; Bach's, 207; Haydn's, 221, 222, 224, 225; Spohr's, 225; German, 232; Italian, 232. Orchestra, the, 121; evolution of, 147-157; early arrangement of, 147, 148; first organized use of, 148; Monteverde's influence on, 149; plan of the contemporaneous, 156-157; transformed in its treatment by Haydn and Mozart, 168. Orchestras, continental town, 61; Hungarian, 84. Orchestration, Wagnerian, 233. "Orfeo," Gluck's, 314, 317, 318, 319. "Orfeo," Monteverde's, 149, 337. Organ, the, 10, 22, 77, 85, 86, 101, 102; first systematic method of playing, 105, 121, 149, 153, 188. Organists, 101, 102; Venetian school of, 102, 209; Roman school of, 104. Organ playing, 115.