For this next part I needed my Father's help. My hand is still in a splint from Mother's day so I was unable to use the strength I needed to whittle away the wood. On the wood part he cut a thin line along the top of the mouth piece and a long groove. I used a red line in the second picture to indicate where to cut. When I was younger he would make the groove longer and put holes along the bark above the grove to create finger holes. Once you are done; carefully slip the bark back over and line it up to where it was before you slipped it off. Your done! This may take a few practice attempts to get it right. As the sap dries out your whistle may stop working, if you re-wet with water it may start working again. You can also use Maple or any other wood that the bark slips freely from. Thank you for reading, good luck and have fun! I leave you with something my Father used to say, and said again while teaching me how to make this willow whistle.
Then I made a steel whistle, and it steel would not whistle.
Then I made a tin whistle, now I tin whistle."