Theodor Rudolph Carl Clewing ( 22 April 1884 – 15 May 1954) was a German operatic tenor/heldentenor, stage and film actor, composer of the song Alle Tage ist kein Sonntag and professor at the Universität der Künste Berlin.

[1] At the outbreak of World War I he volunteered, was first runner and at the end of 1914 he belonged to the parliamentary group under the leadership of Achim von Arnim which called on Reims to hand over the theatre.

Rudolf Binding has literally processed this episode in the story Wir fordern Reims zur Ubergabe auf.

[3] In December 1928 he was appointed associate professor for singing, voice training & practical phonetics at the Hochschule für Musik in Wien.

[3] After the Second World War, Clewing lived in the sanatorium in Glotterbad near Freiburg im Breisgau and spent his retirement in a spa in Badenweiler where he died in 1954 aged 70.

In the Soviet occupation zone his writings Liederbuch der Luftwaffe[6] (published in association with Hans Felix Husadel, 1939) and Adlerliederheft.