At the end of the 1960s, he turned to concert conducting, and for over twenty years he was the principal conductor of the Staatliches Sinfonieorchester and the Philharmonisches Staatsorchester Halle, which he led to national recognition.
[9] In 1950 Koch became Repetitor for ballet, opera and operetta[2] and 2nd Kapellmeister in Meiningen,[3] where he was from then on promoted by the theatre director Fritz Diez.
[3] There, in 1958, he produced the ballet "Kreuzbauer Ulrike" by Carl-Heinz Dieckmann, choreographed by Henn Haas and set during the German Campaign of 1813[12] to the first performance.
[3] In 1961, he realised with the Hungarian refugee Béla Hollai in the West German Göttingen, a joint project between the Göttinger Symphonie Orchester and Stendal with works by Josef Suk, Aram Khachaturian, Carl Maria von Weber and Robert Schumann.
[5] For Alfred Erck, Koch was "endowed with absolute ear, loving the great tone, savouring dramatic moments very well, he duly declared war on inaccuracies, even sloppiness, and was feared by orchestra musicians and singers alike.
His authoritarian style of leadership and dominance with regard to the soloists clashed in Meiningen with the innovations of director Hans Günter Nebel, who was influenced by Walter Felsenstein's musical theatre.
[19] Furthermore, on the occasion of the 1966 Thuringian Music Days, he premiered the Symphonic Poem for Two Pianos and Orchestra by Wolfgang Hohensee with the Berlin pianists Eberhard Rebling and Siegfried Stöckigt.
[18] Koch turned increasingly to concert conducting from 1967[22] and was succeeded by Karl-Ernst Sasse[23] Head and chief conductor of the Philharmonisches Staatsorchester Halle.
[25] Thus, on the occasion of the 1970 Handel Festival, he conducted Beethoven's Tripelkonzert, which was interpreted by the Soviet guest musicians, violin virtuoso Oleg Kagan, pianist Elisabeth Leonskaja and cellist Natalia Gutman.
[27] Moreover, he premiered several contemporary musical works by GDR composers, among others in 1969 Heinz Röttgers Violin Concerto (with Gustav Schmahl)[28] and in 1970 Hans Jürgen Wenzel's "Trassensinfonie".
[35] According to the musicologist Konstanze Musketa, this resulted in "a versatile and powerful ensemble", from which "essential impulses for the musical life of the region" took their starting point.
[23] For the 450th anniversary of the German Peasants' War, it premiered the oratorio "Die Antwort" by Wolfgang Hohensee with a text by Paul Wiens in the St. Mary's Church, Mühlhausen under Koch's direction.
[23] Koch's "authority and negotiating skills", as stated in an obituary in the Mitteldeutsche Zeitung from Halle, also enabled the Philharmonie to make concert tours to the Non-Socialist Economic Area from 1975.
[23] According to the musicologist Achim Heidenreich, in addition to these regular events in the Federal Republic of Germany, which were quite positively noted, German Communist Party organised workers' concerts were also served, which, on the other hand, were not very well received.
[21] Despite not having studied at a conservatoire, he was "open to all artistic and intellectual stimuli, indeed he had a pronounced thirst for knowledge" and was also concerned, for example, with the maxims of historical performance practice.
[21] During his time in Halle, Koch helped GDR compositions to receive Soviet first performances in Moscow, such as the 1965 "Little Music for Orchestra" and the Violin Concerto (with Viktor Aleksandrovich Pikaisen [ru] by Ruth Zechlin[49] and in 1971 the 2nd Symphony by Günter Kochan.
[50] In addition, he premiered Dumitru Bughici's symphonic Suite Pictures from the History of Romania with the Romanian Radio Symphony Orchestra in Bucharest in 1973.
[54] His obsession with power was to be regarded as not unproblematic, under which the then choirmaster of the Robert Franz Singing Academy "Hartmut Haenchen had to suffer increasingly".
[56] Koch's tendential closeness to the state, which had been assessed as a "political vicious circle",[23] led to his resignation in Halle at the end of 1989 after an uncomfortable voting result.
[23] According to Gilbert Stöck, Koch "outwardly affirmed the cultural-political line of the state party with often pithy words".
[5][66] During this period in Halle, the personal union between the artistic and the state management of the orchestra had been abolished; Wolfgang Pfeiffer held the office of director of the Philharmonie.
[7] Olaf Koch also won the Bela Bartok Medal, and an honorary award of the Soviet Union of Composers for the interpretation of commissioned works.