$ grep -5 Composer\ 669 /usr/share/file/magic

# MTM/669/FAR/S3M/ULT/XM format checking [Aaron Eppert, aeppert@dialin.ind.net]
# Oct 31, 1995
# fixed by <doj@cubic.org> 2003-06-24
0       string          MTM             MultiTracker Module sound file
0       string          if              Composer 669 Module sound data
0       string          JN              Composer 669 Module sound data (extended
format)
0       string          MAS_U           ULT(imate) Module sound data

0       string          FAR             Module sound data
>4      string          >\15            Title: "%s"

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строчка с if неоднозначна, мягко говоря.