Tips on Transcribing
On any transcription the VERY VERY first thing to do is to count it out. Get out a few pages of blank manuscript paper and pencil 4 measures to a line. Then count the bars while the music plays. You'll find that you'll soon recognize the different sections and get the arrangement down. Don't rely on sections lasting an even 8 measures, you'll find plenty of occasions where there are 7 or 9 bar sections. And then every once in a while someone will chop a bar in half just before the bridge, etc. I still do at least two "count throughs" (and generally more) before beginning the actual transcription phase.
Always start with the Bass first. In general it's the Bass player's job to tell the truth. There's a high probability that s/he'll be hitting the root on the one beat.
Turn your mids and treble all the way down on your player and turn the bass all the way up.
At first, you will: hear the note, stop the recording, hum the note, find it on the keyboard and then write it down. Then you'll move on to the next note.
As you gain more expertise at hearing a single bass note (and that can be tricky, lots of times notes get obscured by other instruments or notes in the arrangement) your transcriptions will begin to come more easily. As time goes by, you'll begin to recognize Bass phrases and "clichés" and you'll be able to move from the "single note recognition" level to the "phrase recognition" level. (It won't happen overnight though, and it'll only happen if you keep transposing regularly - treat your ear like a muscle - you've got to keep working it out).
Another really useful tip is: SKIP OVER THE HARD PARTS! Do all the easy stuff first (this is not only true for transcribing the Bass part, but for all parts). Since you've already lined it all out your manuscript paper, you don't have to beat your head against the wall for hours just trying to get one lousy little note or phrase. Move forward, don't waste your time. Do all the easy stuff first and then come back to the hard parts later. You'll generally find that one of the following things will have happened by the time you've transcribed the easy bits all the way to the end of the song:
1) You've found a section later on that's exactly the same as the hard part earlier, but (for recording quality reasons) is easier to hear and therefore transcribe.
2) Your subconscious has been working on the problem behind the scenes and has already come up with the answer.
3) You can come back and listen to the problem area with "fresh ears".
Next transcribe the melody and/or solo. As mentioned above, at first you'll have to do this note-by-note (this will be tedious, but you gotta walk before you can run, and you gotta crawl before you can walk). With time, you'll begin to recognize full blown phrases and mimic them with ease (for some that can take several years to move from the crawl to the run - but with practice, I guarantee it will happen).
And now for the chords. You've already got the bass line and the melody. In general the melody will contain one or more chord tones. Determining which melody tones are chord tones and which melody tones are passing notes can be accomplished by taking into account the hierarchy of the beat. (A melody note falling on beats 1 or 3 has a high probability of being a chord tone, whereas a melody note falling on beats 2 or 4 has a high probability of being a passing tone. Another factor to take into account is emphasis, ie. if a certain note is emphasized, it has a high probability of being a chord tone) This might not give you the EXACT chord in the underlying harmony, but it will help you to identify the basic chord qualities.
If you have an understanding of theory and chord progression conventions, you can use logic (based on your bass and melody transcriptions) to infer the chord extensions and alterations.
As far as voicings are concerned, take into account the conventions inherent in the genre of music you're working in. Chances are you won't be far off. Then play your chords against those on the recording and see how they stack up. You might notice some differences, but you'll probably also notice a lot of similarities.
In order to find exact harmonies (rather than intellect-based theorizing) you have to cultivate the ability to selectively screen out everything except the note you're trying to hear.
Go slow, one chord at a time, one note in the chord at a time. Once you've "got" the note - stop the recording and HUM THE NOTE before searching for it on the keyboard. While humming the note begin searching on the keyboard for it.
Once you've found it, go back and play the recording to that point to double check. If you're certain that you nailed it, scribble it down and move to the next note.
Keep in mind that even though the basic progressions may remain relatively constant throughout a tune, in Jazz there's a tendency to get a little freakier as the song progresses. Expect more alterations and extensions in the middle of the tune than the vanilla stuff used to state the head.
Even Bill Evans doesn't play his famous rootless chords the same way all the time. Those voicings are just a springboard to serve as examples of how to build your own chords that suit the piece.
Finally, what is the real purpose of doing transcriptions? Yes, they build the ear. Yes, they allow us to cop some of our heroes' riffs. But the most important reason to transcribe is that it gives us an insight into the thinking processes involved and gives us clues as to how to use those same principles to create OUR OWN music.
Without taking the final step of analyzing the whys and wherefores of how the player constructed his/her improvisations, etc and HOW WE CAN USE THOSE PRINCIPLES TO CREATE OUR PERSONAL MUSICAL VISION, we will have missed the point completely.