Complex sentence: With Paris as his base he made frequent concert tours to a number of German cities: on 12 April 1773 he appeared in Frankfurt am Main, a year later in Augsburg, and in 1775 he ventured as far as Saint Petersburg in Russia.
Split into simpler sentences: With Paris as his base he made frequent concert tours to a number of German cities. On 12 April 1773 he appeared in Frankfurt am Main, a year later in Augsburg, and in 1775 he ventured as far as St. Petersburg in Russia.