Transcribing music, particularly when it involves improvisation can be near to impossible. The problem is the notation system handed down to us from the middle ages. It has been deficient in fully notating music for centuries -- since the time of plainchant Gregorian Chant, for which it was designed. It is always possible to transcribe a general sense of the music, but not always possible to notate all of the nuance. Again, there is not a piece by Bach or Beethoven or Mozart or Brahms or Chopin that "accurately" transcribed to truly indicate their intentions.
A particular part of the problem involves instruments that can play "in the cracks" (micro-tones) and such. Our basic notation system was not designed for more than 12 notes (it was actually originally designed for 7 note scales (the church modes) but was reasonably adaptable to a 12 note tonal system.) There are notation systems and additions that can overcome some of these deficiencies, but that is a whole other learning curve (like about 12 symbols for Sharp and Flat indicating how Sharp or how Flat), particularly when next to no one is using them.
Rhythm notation is also filled with problems, particularly in jazz and rock solo transcriptions -- but again that has been going on since a year and a half
after rhythm notation was invented.
Also, some of what James Brown or any improviser has created may be equipment specific or may be possible on different equipment but using totally different techniques. Distortion unit A may require a different set of notes to be played than Distortion unit B to get the same basic sound.
As such, any solo transcriptions that you use should be used in conjunction with the actual recording. To bad we don't have recordings of Bach, and Beethoven, et. al.
But, aahhh, that is the Joy of Music, there are always new challenges.
Of course, as digital technology gets better, there may soon be a computer notation program that can "read" and transcribe an audio part (there are some that will do for single line melodies, but they have difficulty with chords.)