This is a parting song which works well at the end of a choir session or workshop. 
 
The Soprano and Bass parts are simple and quick to pick up. The Altos and Tenors have some less obvious harmonies (that provide the scrunch!) that take a bit longer to learn, so this is not a quick one to attempt in the last  10 minutes! It's usually taken me about 40-45 mins to teach and then I let the group sing it over and sink into it to say goodbye. People seem to love singing it, and it's definitely worth taking time to get the notes right. 
 
Challenge rating: Medium