I'm not sure whether it's my 'M' or not, but I happen to have a question ready, so (with implied permission, and gladly acknowledging mercia's revelation of the key word):
How might a type of vine; a type of goose; a breed of cat; and a strain of a viral infection lead you to four examples of 'M'?
M is not the name of a composer, but the chap in question did indeed write, among many other works, a number of marches, the titles of four of which are suggested by the clues.
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