Rudi,
I'm addicted to band in a box because it's there visually with the chord chart, I can pull up the tab or notation or fretboard view in seconds and I've got the whole song right in front of me. But when I walk away or close the program my mind goes blank. I love the program and it's a crutch.
You are in the position of playing a great deal of songs regularly as you play out often. All those songs are stored in your muscle memory so you don't have to think about them as much. 100 songs memorized will take a performer very far and they'll be less in wanting of learning new material. Older less used material seems to fade away. I used to be like that with my blues and rock cover bands. I got very very good at playing songs of others and the crowds really weren't interested in my originals.
The thing is you....think. Many are too quick to absorb themselves with cell phones and facebook and what's on tv all outside distractions which block the "inner ear/inner voice" from getting a chance to get out. It's why when you have some free time sitting somewhere you can work out musical ideas where as others can't/don't.
Allistar,
There isn't one or two 12 bar blues progressions that the blues is written with. There are actually 60+ variations (not key not tempo or "style" but actually different ways to approach it. As well there are 16 bar blues progressions (rock this town - stray cats) 8 bar and even 9 bar blues progressions. That's not even including the Gospel/soul progressions that often find there way into blues settings. As well there are other devices aside from simple substitution to rewrite progressions. So if you find a commonality with another song in regards to the progression there are ways to rewrite it in a manner that seems less common.
Progressions are not the only way to write music, even popular music. Progressions can be laid on after the fact if the melody is strong enough. Good melodies stand on there own without the need of supporting instruments. Writing music is much like writing a short story. There are plots and recurring themes. And sometimes it's not what you say as much as how you say it that makes the difference. That being said while some mathematicians speculate that given the limited number of combinations of our twelve tone system and metering all the songs that could be written may already have been. We just don't recognize them as such.
I've brought this up in the past but I'll bring it up again. I used to be a studio musician. Mostly performing jingles and occasionally supporting a local "singer" on there way to fame, fortune or obscurity. The producer was the writer. The trick about jingles is make them "seem" like someone has heard it before. So it falls on the ears more naturally the first time out and is remembered by consumers more quickly. The way to do this is to take a song that may have been modestly popular and re write it. (key, progression, substitutions) so it doesn't sound like the original. Often one would juxtaposition two songs like the beginning of one and the end of another. It does take work and imagination but it's a cookie cutter operation and time is of the essence.
....More