Born in Duisburg, Maehder studied in Munich and Berne, where his professors included Thrasybulos Georgiades and Stefan Kunze (musicology), Günter Bialas (composition), Arnold Metzger (philosophy), Klaus Lazarowicz (theatre history), August Everding (opera production) and Walther Killy (German literature).

In 1990 he contributed to the creation of the Fondo Leoncavallo at the Biblioteca Cantonale in Locarno, Switzerland, where he co-organized five international symposia between 1991 and 2006.

[1] After his retirement from Freie Universität Berlin he taught musicology and libretto history at the Department of Italian Studies of the Università della Svizzera italiana in Lugano, Switzerland.

Maehder has organized international conferences on Giacomo Puccini,[4] Ruggero Leoncavallo, Giacomo Meyerbeer, Giuseppe Verdi, Richard Wagner and Gaspare Spontini, Bohuslav Martinů and Sylvano Bussotti,[5] on libretto history and the methodology of opera research in Italy (Torre del Lago 1983 e 1984; Ravenna 1984; Villa Vigoni, Loveno di Menaggio/CO 1993; Maiolati Spontini/AN 2007, Roma 2016), in Germany (Bad Homburg 1987; Berlin 2000; Berlin 2001; Leipzig 2004; Münster 2006), in Switzerland (Fondo Leoncavallo, Locarno/TI 1991, 1993, 1995, 1998; 2006), in Austria (Bregenz 2002; Salzburg 2002), in the Czech Republic (Praha 2000), in Russia (St. Petersburg 1994), in the Republic of China/Taiwan (Taipei, 2005; Taipei 2006; Taipei 2008; Taipei 2013).

[1] Since 1994 Maehder has published a series of musicological monographs under the title Perspektiven der Opernforschung in collaboration with Thomas Betzwieser.