Use xmp to play the chiptune to stdout as wav,
boost the volume with sox (if needed),
encode it with oggenc
1 | xmp -d wav -c filename.mod | sox -v1.5 -t wav - -t wav - | oggenc -o filename.ogg - |
or if you want to convert all chiptunes in a directory:
1 2 3 | for i in *.mod *.xm; do xmp -d wav -c $i | sox -v1.5 -t wav - -t wav - | oggenc -o ${i%.*}.ogg - done |