He was the musical director of the 1998 Eurovision Song Contest, the final edition of the contest to date with a full orchestra present. Koch conducted the BBC Concert Orchestra for the intro music, the interval act "Jupiter, the Bringer of Joviality," and the French entry, "Ou aller" by Marie Line, which initially was performed entirely to a backing track before the decision was made to incorporate the orchestra's string section. Thus, although it saved Koch from being one of the handful of Eurovision musical directors who didn't actually conduct any competing entry, he also didn't take the customary conductor's bow prior to the French performance.