A bit more thought about this topic suggests that Seume's thesis
that evildoers do not sing becomes plausible as soon as "evil"
is defined with etymological precision as "unethical" or "immoral",
i.e. as "anti-social", as the refusal - or inability - of the
individual to be integrated into society, e.g. the bank robber.
The circumstance that the bank-robber has no music suggests that
music, song, may be an inherently communal activity. "Now we all
sing together!" Perhaps even the desolate loneliness of the
romantic bard, epitomized, e.g., in the Schubert-Mueller Winterreise
and Schoene Muellerin or in Beethoven's An die ferne Geliebte
should be interpreted not as anti-social, but as meta-social,
an expression of the individual's longing for, of his need for
society. When one then considers the personality of Th. Mann's
Tonio Kroeger, the artist as the quintessential outsider and
therefore potential criminal, one suspects the wheel to have
come full circle. Accordingly, music, song, and especially
the great art songs of the 19th century, virtually all of them
songs of isolation and loneliness, may be construed as an
expression of the individual's need and longing for society,
the sublime "whistling in the dark" of the "lost" soul.

The dialectical antithesis of Seume's assertion that evil-doers
do not sing, would assert just the opposite: that music and
song, appealing as they do to the "inner" ears of the musicians
and the hearers, serve to separate the individual from society,
are therefore inherently "unethical" or "immoral", subversive of
the social fabric, and as such constitute the ultimate solvent
of the social continuum, validating Tonio Kroeger's thesis that
the artist is by nature anti-social, that art is a species of
crime. Something to think about.