Are you learning a new tune? Want to know how to figure out what key/mode it's in? Here's a handy guide to help out. Step 1: Match up the number of sharps to determine the name of the key signature of your tune. Step 2: Find the name of your home note (where the tune comes to rest). Hint: It's usually the last note of the tune. Step 3: Does the home note match the name of the key signature? If you have a match, you're in that major key and no further steps need to be taken.