TromboneChat

Hi, playing jazz I try to transcribe as much as I can.

I think it's a great exercice for ear training, absorbing language, understand how a solo works and technique too.

1st I want to know if what I'm doing is alright.

At the level where I'm at, I decide to transcribe a solo that I know I can find an accurate transcription on the web because I have very bad ears.

Let me explain, first I transcribe and write down thé entire solo, then I check with the transcription I've found on the web for error.
Then I transcribe another time but without writin', just memorize phrase after phrase and just check the paper for errors every chorus.

But harmony is nightmare for me, chords are played too short, change too fast and I can't hear clearly in contexte with the others instruments playing in the same time.

That’s a solid method! It’s always good to have a reference to double check against as you improve your skills. And the important thing is that you’re still doing the transcription yourself, as you are. And always best to do this with the horn in your hand, whether or not you then write it down (I always do!) or commit straight to memory.

Harmony is definitely trickier. Some points to remember:
Generally the harmony under the solo is the same as the harmony elsewhere in the song. Try listening the whole way through the song and writing it out along with the form, as it may be clearer another time.
Listen to the BASS, first and foremost. It’s bound to play at least one root note per chord, 90% of the time. Then a guitar if it’s comping. A lot of what the piano does can be more decorative, and can often use passing chords that potentially obscure the underlying harmony for you.
Familiarize yourself with some of the most common forms of changes - blues (of different lengths), rhythm changes, trad jazz, etc. It’s possible, and even likely, that you can make an educated guess about the harmony right off the bat.
Invest in an app like Transcribe! to help you. You can slow down to help hear lines more clearly, and there’s a spectral analysis to show what tones are more prominent (but never really on this. Always verify). Top tip - shift the whole thing up an octave, and the bass becomes clear as day!

Mostly, keep going! Transcription, like any other skill, takes practice to improve. The more you do, the better you get.

Also, this website has TONS of excellent advice on all aspects of playing jazz that is super valuable. It’s a veritable goldmine. https://www.jazzadvice.com/?s=Transcription

Your method sounds just fine. I’ve always found that being able to sing it first is very helpful. Now it’s so easy to put your headphones on and listen on repeat while you’re driving, riding, or whatever. When I sit down with the horn I already have the majority of it in my head. This makes it so much easier for me.

Your method sounds good to me. Just keep doing it.

I consider myself to have bad ears as well. All of this stuff comes with time and work. If you put in the work you’ll see the benefits.

Also, harmony is difficult. You’ll start to see and hear patterns the more you do it. Arranging helped me a lot too. You get your ears out of the solo and see what’s going on during the song (melody).