The second half of the sixteenth century has been aptly called ‘The Golden Age of Ecclesiastical Music.’ Further progress was impossible along the line of vocal counterpoint brought to such astounding perfection by Palestrina, yet the Palestrina style found zealous imitators for a half-century at least after the passing of the great Roman master. But the spirit of the Renaissance, now rampant in every field of human thought, refused to be held in check by church doors, and the glories of the ‘Golden Age,’ the products of an art rejoicing in the full maturity of its power, were almost immediately followed by a period of decadence, in which secular sentimentality was mingled in strange fellowship with what remained of the majestic devotional style of the old masters. The triumphant progress of secular music, instrumental as well as operatic, soon broke down the opposition of the ecclesiastical purists, and after Allegri the Palestrina style practically disappeared. Gregorio Allegri (about 1580-1652) is remembered now almost wholly by his celebrated _Miserere_ for nine voices in two choirs, which is considered to be one of the finest compositions ever conceived for the Roman service. Until recently at least, it has been sung annually during Holy Week at the Sistine Chapel, where it was prized as so rare a treasure that to copy it was punishable with excommunication.[37] Up to the year 1770 only three copies are known to have been legally made. In that year, it will be recalled, the fourteen-year-old Mozart wrote it down with marvellous accuracy from the memory of a single performance. Much of the ineffable sadness of this piece, which, as it is performed in the Sistine Chapel, has always aroused the unbounded enthusiasm of musicians, is said to be due to certain traditional embellishments or florid passages which were introduced in the form of elaborate four-part cadenzas to take the place of the simple endings of some of the verses. Mendelssohn, in a letter to Zelter during his Italian journey in 1831, described in great detail the music of these beautiful _abbellimenti_. Of one of these he says: ‘It is often repeated, and makes so deep an impression that when it begins an evident excitement pervades all present.... The soprano intones the high C in a pure, soft voice, allowing it to vibrate for a time, and slowly gliding down, while the alto holds its C steadily, so that at first I was under the delusion that the high C was still held by the soprano. The skill, too, with which the harmony is gradually developed is truly marvellous.’