This severity was afterwards relaxed, until the oboe was used alone or as the principal wind instrument, generally to support the voice or to strengthen the harmony. It was {CHURCH MUSIC.} (284) allowed to assert its own individuality at a later time, but this could only be when it retained its proper place among the different combined wind instruments. Flutes were only rarely used to replace the oboe in soft passages; there were no clarinets in Salzburg. Bassoons served, as a rule, only to strengthen the bass; in various places where they, like the violoncello, were treated with some degree of independence it was so indicated in the score. Also when the tenors were associated with the wind instruments to complete the harmony they were supported by the bassoons. The horns at first closely followed the trumpets, but gradually attempts were made, by the use of sustained notes, to produce the sound effects peculiar to this instrument. The freer treatment of the wind instruments passed to the church from the opera, and those pieces which were altogether more freely treated than masses, prepared the way for the change. The orchestra of Mozart's two last Litanies is just as elaborate and careful as that of his operas, and the later one does not only employ obbligato solo instruments, but in many of its sections approaches modern instrumentation. We are unfortunately in considerable ignorance as to what masters were studied by Mozart. What has usually been said of his diligent study of Bach, Handel, and the Italian masters, is neither demonstrable nor probable. There would scarcely be much opportunity at Salzburg for the study of any but Salzburg or south German musicians. It is well known that some of these, such as Eberlin, Michael Haydn, and Adlgasser, were earnestly studied and highly esteemed by Mozart. But he first became acquainted with Sebastian Bach[56] through Van Swieten in Vienna, although he may have come across detached organ or pianoforte compositions in Salzburg. He heard Handel's oratorios as a boy in London, but that was all, and even at Mannheim he took no great interest in the "Messiah." It was again Van Swieten who led him to this master. We may grant a stronger influence to the Italian masters, {ITALIAN INFLUENCE.} (285) although the older Italian church music was only exceptionally used at Salzburg.