Ok, This is a test to see who can answer this in a way that this doofball can understand. The winner gets a prize. Over the last few days in my bandless state, I have opened up my loved Bass Grimoire book. Now keep in mind I understand absolutely nothing in this book other than the last pages that have the fretboard and every damn scale I can think of. Ok, I know whole and half step too. So, I am learning some scales again. Right now, learning the Major scale in all modes. Never gave it the time of day and, honestly, the major scale seems like one I always find myself in naturally after seeing the patterns--it is either this or minor pentatonic. Anyway, I do not understand the importance of the modes. For example, I've got I-V down. In the key of A. I have not memorized the notes nor the entire fretboard. Now, putting this to use: A song in the Key of A. How do these modes come into play? Can one mode work in the key of D? How and why? Best answer gets prize!!! A real prize.