Is that the sapwood? If so, and you have enough depth, go down to the heartwood, that crack might just be in the sapwood. If it is, be sure to seal the back when you get it chased, the stave might still be a little green. Is it a board? Sometimes you can superglue and clamp the crack back together and it will hold. Sinew will definitely work, rawhide might as well, and you could wrap with thread too.
Steaming works fine, but I prefer dry heat...unless the wood is not seasoned.
George