The flute and lute were his favorite instruments, and he used the latter always in accompanying his own singing. John Walther, a contemporary composer who later aided Luther in the writing of church music, has left us this testimony: "It is to my certain knowledge that that holy man of God, Luther, prophet and apostle to the German nation, took great delight in music, both in choral and figural composition. I spent many a delightful hour with him in singing; and ofttimes I have seen the dear man wax so happy and merry in heart over the singing that it is well-nigh impossible to weary or content him therewithal. And his discourse concerning music was most noble." In his "Discourse in Praise of Music," Luther gives thanks to God for having bestowed the power of song on the "nightingale and the many thousand birds of the air," and again he writes, "I give music the highest and most honorable place; and every one knows how David and all the saints put their divine thoughts into verse, rhyme, and song." Luther had little patience with the iconoclasts of his day. He wrote in the Preface to Walther's collection of hymns, in 1525: "I am not of the opinion that all sciences should be beaten down and made to cease by the Gospel, as some fanatics pretend, but I would fain see all the arts, and music, in particular, used in the service of Him who hath given and created them." At another time he was even more emphatic: "If any man despises music, as all fanatics do, for him I have no liking; for music is a gift and grace of God, not an invention of men. Thus it drives out the devil and makes people cheerful. Then one forgets all wrath, impurity, sycophancy, and other vices." Luther loved the Latin hymns that glorified Christ. He recognized, however, that they were so permeated with Mariolatry and other errors of the Roman Church that a refining process was necessary in order to rid them of their dross and permit the fine gold to appear. Moreover, the Latin hymns, even in their most glorious development, had not grown out of the spiritual life of the congregation. The very genius of the Roman Church precluded this, for church music and song was regarded as belonging exclusively to the priestly office. Moreover, since the entire worship was conducted in Latin, the congregation was inevitably doomed to passive silence. Brave efforts by John Huss and his followers to introduce congregational singing in the Bohemian churches had been sternly opposed by the Roman hierarchy. The Council of Constance, which in 1415 burned the heroic Huss at the stake, also sent a solemn warning to Jacob of Misi, his successor as leader of the Hussites, to cease the practice of singing hymns in the churches. It decreed: "If laymen are forbidden to preach and interpret the Scriptures, much more are they forbidden to sing publicly in the churches."