Here's what you need to import just the song and player from the .gb file - you chop off the first 0x4000 (16K or 16384) bytes. If you're on OSX or a *nix system, you can use dd to do this like so:
dd if=fruitless.gb of=fruitless.bin bs=1k skip=16
That will take the source ("if") file and copy its contents into the destination ("of") file, using blocks of 1KB, but skip the first 16 blocks.
If you INCBIN that .bin file, it should hopefully work.
You can also just INCBIN the .sav, as they helpfully do the chopping for you - you may want to just copy the first 16KB though, which you can do like this:
dd if=fruitless.sav of=fruitless.bin bs=1k count=16