Martin Janus

Martin Janus, also recorded as Martin Jahn, was a Silesian Lutheran church musician, educator, pastor, and hymn writer born about 1620. After receiving a theological license, he served as precentor of two churches at Sorau. Around 1653 he became rector of the Evangelical school at Sagan and precentor at a nearby church, responsibilities that joined teaching, worship leadership, and music.

Janus became pastor at Eckersdorf around 1664. In 1668 an imperial edict expelled Evangelical pastors and teachers from the principality, disrupting his ministry amid the confessional pressures that followed the Thirty Years' War. Later accounts place him as a precentor at Ohlau, where he is believed to have died around 1682. Some details of his chronology remain approximate because the surviving biographical record is limited.

His principal hymnological legacy is Jesu, meiner Seelen Wonne, written in 1661 and printed in Christlich Herzens Andacht in 1665. The long devotional hymn presents Jesus as the believer's delight, consolation, strength, and treasure. Bach selected two of its stanzas to close the two parts of BWV 147. Janus wrote those German words; he did not write the later English poem commonly called Jesu, Joy of Man's Desiring.