Ear training, and physical memory, or muscle memory are key I think.
I'm big on positioning. So, for example if we are playing in C major, I may have my middle finger on the root C, and I know where all the other notes in that Key, or Chord are under my fingers, in one posistion. That also includes knowing what they sound like. So, remembering a passage, a fill, a whole song, or whatever, comes quicker. It's like the physical muscle memory, and the mental musicial/interval memory, go hand in hand.
That's one of the reasons I don't like Drop D style tuning. Sometimes it may be fun to have the octaves running parallel, for tapping or something. But I like my intervals where they are supposed to be, because it's not only your fingers, but your brain that should know where those tones are. In my band we tune to low C#, my bass is tuned C#F#BE, so it's still in fourths.
I'm big on positioning. So, for example if we are playing in C major, I may have my middle finger on the root C, and I know where all the other notes in that Key, or Chord are under my fingers, in one posistion. That also includes knowing what they sound like. So, remembering a passage, a fill, a whole song, or whatever, comes quicker. It's like the physical muscle memory, and the mental musicial/interval memory, go hand in hand.
That's one of the reasons I don't like Drop D style tuning. Sometimes it may be fun to have the octaves running parallel, for tapping or something. But I like my intervals where they are supposed to be, because it's not only your fingers, but your brain that should know where those tones are. In my band we tune to low C#, my bass is tuned C#F#BE, so it's still in fourths.