If you have read "How to Learn Music" under Tips, and you follow all the steps and practice daily, your songs will memorize themselves in no time at all. But sometimes things get in the way. We don't have enough time to practice, we get lazy and skip most of the steps and just sing through the song a bunch of times without much thought, we have to learn a song at the last minute….And then we realize there is a performance coming up, and the song isn't memorized yet!
Forced memorization is not ideal, but it can get you through a tough time. For example, during my doctorate, I was given the option to take an exam to test out of the required orchestration class (who the heck wants to take orchestration as a singer?). I knew nothing about orchestration (why would I?). My roommate let me borrow her textbook, and over the course of two days, I memorized all the important parts bit by bit, and I aced the exam. About two days later, I promptly forgot everything I had learned. Conversely, I have complete operas that I learned and memorized slowly and correctly over 10 years ago that I could probably pick up today and have re-memorized in 2 or 3 days. So I highly recommend taking your time and learning music the slow and thorough way.
So what do you do when you need a song memorized ASAP?
Start with the text. I find that the memorizing part of my brain works really well just before bed and first thing in the morning, and that is when I recommend doing the following.
1) Divide the song into sections of around four lines each.
2) Take the first line of text and say it five times (1-1-1-1-1). Now take the second line and do the same thing (2-2-2-2-2). Put them together and repeat )1-2-1-2-1-2-1-2-1-2).
3) Now take line 3 (3-3-3-3-3). Now try 1-3 together (1-2-3-1-2-3-1-2-3-1-2-3-1-2-3).
4) Now line 4 (4-4-4-4-4). Now put 3 and 4 together (3-4-3-4-3-4-3-4-3-4).
5) Now try 1-4 (1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4).
6) Did you forget something? Let's say you forgot the beginning of line 4. Do 3-4-3-4-3-4-3-4-3-4. Now try 1-2-3-4 again.
7) Once you are comfy on the first section of the text (which may be more or less than four lines), take the next section and do the same sort of patterns. Then put them together. Any time you forget the beginning of a line, take the line before, connect the two, and add more lines to them until you can say the whole text without thinking.
8) Go to bed. Think about any lines you can remember while you are falling asleep. In the morning, wash, lather, rinse, repeat. Then do it again before bed. You will be amazed first off at how annoying this process is, but more important, how quickly it works.
Now that you have the text memorized, you can use the same pattern as above using both the text and the music, taking the music section by section. You'll be golden in no time!