| Muscalu, Stelica | Stelica Muscalu | Composer, Musical Director | 2006 - 2009 | 2 | |
| Müller, Gert | Gert Müller | Composer, Dramaturg | 1981 - 1996 | 3 | |
| Mankovecký, Róbert | Róbert Mankovecký | Composer, Dramaturg | 1993 | 2 | |
| McCarthy, Michael | Michael McCarthy | Composer, Dramaturg | 2012 - 2020 | 3 | 1 |
| Michaïlidis, Giorgos | Giorgos Michaïlidis | Composer, Director | 1984 - 1985 | 4 | |
| Miler, Eduard | Eduard Miler | Composer, Costume Designer, Director | 2004 - 2015 | 7 | 1 |
| Meissner, Hjalmar | Hjalmar Meissner | Composer, Conductor, Musical Director | 1889 - 1919 | 6 | |
| Meyers, Emerson | Emerson Meyers | Composer, Conductor | 1965 | 2 | |
| Mihály, András | András Mihály | Composer, Conductor | 1990 | 2 | |
| Munkeby, Jørgen | Jørgen Munkeby | Composer | 2006 - 2011 | 5 | 1 |
| Molina, Nicolás Posse | Nicolás Posse Molina | Composer | 2001 | 1 | |
| Madin, Chris | Chris Madin | Composer | 1999 | 30 | |
| Maier-Waelde, Ingeborg | Ingeborg Maier-Waelde | Composer | 1969 | 1 | |
| Mandel, Ellen | Ellen Mandel | Composer | 1994 - 1997 | 2 | |
| Martinig, Aldo | Aldo Martinig | Composer | 1984 | 1 | |
| Marzewski, Lucjan | Lucjan Marzewski | Composer | 1989 | 1 | |
| Mazzocchetti, Germano | Germano Mazzocchetti | Composer | 1993 - 2019 | 42 | |
| McCracken, Everett | Everett McCracken | Composer | 1928 | 2 | |
| Merz, Horst | Horst Merz | Composer | 1992 | 1 | |
| Migliardi, Mario | Mario Migliardi | Composer | 1974 | 2 | |
| Mufti, Uns | Uns Mufti | Composer | 2006 - 2012 | 4 | |
| Mezzacappo, E | E Mezzacappo | Composer | 1937 | 1 | |
| Mikula-Proksa, Marzena | Marzena Mikula-Proksa | Composer | 1979 | 1 | |
| Meyerbeer, - | - Meyerbeer | Composer | 1892 | 1 | |
| Mascagni, - | - Mascagni | Composer | 1892 | 1 | |
| Michiels, - | - Michiels | Composer | 1892 | 1 | |
| Ming-chu, Maggie Shum | Maggie Shum Ming-chu | Composer | 2001 | 1 | |
| Maćkowiak, Janusz | Janusz Maćkowiak | Composer | 1957 | 1 | |
| Madzharov, Nikolaj | Nikolaj Madzharov | Composer | 2006 | 1 | |
| Mullin, Bronwen | Bronwen Mullin | Composer | 2011 | 1 | |
| Milner, Johnny | Johnny Milner | Composer | 2007 | 1 | |
| Monteiro, Bruno | Bruno Monteiro | Composer | 2009 | 1 | |
| Müller, Maximilian | Maximilian Müller | Composer | 2010 - 2011 | 8 | |
| Mozart, Wolfgang Amadeus | Wolfgang Amadeus Mozart | Composer | 1879 - 2008 | 7 | 1 |
| Mendelssohn-Bartholdy, Felix | Felix Mendelssohn-Bartholdy | Composer | 1879 - 1916 | 18 | |
| Moszkowsky, Moritz | Moritz Moszkowsky | Composer | 1885 - 1888 | 3 | |
| Møller, C.E. | C. E. Møller (C.E. Møller) | Composer | 1889 | 1 | |
| Mendelssohn, Arnold Ludwig | Arnold Ludwig Mendelssohn | Composer | 1898 | 1 | |
| Massenet, Jules | Jules Massenet | Composer | 1900 - 1917 | 4 | |
| Moskowski, Moritz | Moritz Moskowski | Composer | 1910 | 1 | |
| Mahler, Gustav | Gustav Mahler | Composer | 1979 - 2020 | 11 | 1 |
| Moe, Ole Henrik | Ole Henrik Moe | Composer | 1996 - 2006 | 2 | |
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