"What is the least time-consuming and least difficult way to learn to duplicate a piece of music note for note and play that piece of music on a software emulation program of a B3 organ with a MIDI keyboard controller?"
OK, that
is different...
"I sometimes look at the sheet music for some guitar parts both in standard notation and TAB. I am not skilled enough to play that part live and up to speed without studying it, nor would I typically want to. Sight reading for guitar or other string instruments is not a simple skill to learn but people do it every day.
... and you've moved the goalpost again.
Some instruments lend themselves to written notation. The piano and organ are excellent examples of this, because there aren't those many "moving parts" to work with. Notation that captures the notes, pedaling and dynamics does a good job capturing all the elements of the performance. For keyboard instruments, it's helpful to have accurate fingering (
i.e.,
which finger to use on the keys, but this may need to be modified depending on the player's reach.
On the other hand, for a lead guitar there can be a lot on musical information that's not captured by traditional notation, and is difficult to capture in even in tablature. Some things aren't captured in notation, like amp settings. The best way to learn is to treat the tablature as a general roadmap, in combination with a recording of the performance.
The best notation is the one that allows you to accurately recreate the original performance. Since you're talking about being able to play live, you're not going to use that notation while performing the music. Notation is only a temporary tool.
Sight reading is
hugely useful. But you don't need to be able to sight read in real time in order to use written notation. You
do need to know the basics. For example, an F# in a key signature means
all Fs in the music are played as F#s, and an accidental stays in effect for the duration of the bar. Beginning players often add in accidentals to all notes to remind themselves.
Obviously, learning to sight read will allow you to perform lots of new material faster. But if you take your time, you can memorize music that's notationally difficult to read without being able to sight read it in real time.
Being able to sight read means that you can spend more time learning the music instead of deciphering the notation.
Music theory can be
extremely helpful for memorizing a piece. For example, if you see chordal arpeggios, harmonic progressions, pentatonic scales and so on, the piece of music becomes something more than hundreds of random notes to learn, but instead a realization of musical ideas within a context. The larger the chunk, the less information has to be memorized.
Once you've memorized chord shapes on an instrument, it's easy to see them in notation and tie them to the muscle memory of where they are on your instrument.
As far as learning parts quickly and accurately, it boils down to the same thing for every instrument:
1. Have an accurate representation of the performance (standard notation, tab,
etc.).
2. Be competent in the techniques required to perform the piece (fingering, bends,
etc.).
3. Slow and accurate performance of the music, broken into small, learnable parts.
4. Playing the parts so they connect smoothly.
5. Once a slow, accurate performance is obtained, progressively adding speed until it's up to tempo.