Tony's right. I "pull them" from my past memory banks. If I get lucky, most of the words and music just sort of "come back" in stride, but sometimes, I have to really WORK for it!
I've found that the key to successful memorization is in 2 parts:
1) Lyrics - we've discussed this before, but if you WRITE out the words, then READ them out of rhythm(spoken, out loud) ... they seem to stick in your mind better. The better the lyric, the easier it will be to memorize, because it will make sense.
2) Music - Memorize the CHORDS only. Train your ear to understand and recognize the intervals. Many patterns repeat and follow logical progressions, like the classic:
I - vi - IV - V7 that made up UMteen-thousand 50s and 60s ballads.
Once you recognize where the chords are going - you can find the melody much easier.
I also believe that a good solid understanding of bass lines helps you to better understand the entire arangement. That's why I love playing my own manual lines as much as possible. The bass line is like the road map to the song ..... it will lead you in and out of all the changes!
I only have about a dozen charts on my laptop. These are songs that somehow get lost, and forgotten ... I don't even think of them unles they are requested. I can't tell ytou the last time I even accessed one of them. My restaurant gigs ( happy now???
) are pretty predictable. They are mostly Italian places, so Sinatra, Bennett, Martin ..... get requested alot. There's not a whole lot of oddball stuff that I throw at them during dinner. It's AFTER dinner that I start to get creative!
Last night I did Taxi(Harry Chapin), AND the sequal (did you even KNOW there was a sequal?), The Loadout(Jackson Brown), But you know I love you(Kenny Rogers & 1st Edition) .... I was havin' a ball !