Just one, drain. If you use the same approach to mathematics as MTed suggests to music theory, by the time you have enough knowledge to do what you want to do, the IRS will have you in jail for failure to pay taxes for the last 10 years, the lot for your new house will have been bought up by the city for a new strip mall, and your heirs won't get a dime because lawyers will have usurped your estate to pay their fees in trying to divide it up.

And Merle, that enharmonic submediant you play on the third beat of bar 41 is proportionally dissonant to the atonal triad suggested by the melody superimposed over the subtle counterpoint inherent in the next beat. I suggest A7 instead of A. Otherwise, the tune is a smash. Love ya man, and remember, leave no turn left unstoned. All the best, Willie.