Marko first I like the composition...nice stuff.
Jazz is somewhat my thing......so I feel a little qualified to make comments although take what I say with a grain of salt. It is whether it sounds good to you that is the main thing.
Like William said, I can hear that these are samples obviously but it does not bother me much, as the composition almost lends itself to that. It is a quirky little piece with lot's of possibilities.....I hear portions of this composition in a film soundtrack, spread out over a scene....good stuff.
To my ear, the drums....all the elements of the kit..... and bass need attention to the space they occupy as far as separation, panning and EQ and reverb. The drums, bass etc all seem to be sitting dead center fighting for the same space.
For me you are right about the bass. It definitely needs remixing.....it is too loud and the tone of it needs help, a bit too boomy. Roll off some lows, maybe grab some mid's and take it back in the mix a little. It sounds more like an orchestral double bass rather than a jazz double bass if that makes any sense at all? Maybe since an upright in a jazz band is likely to be close mic'd or even have a pickup...or both. This would allow one to really dial in the EQ on it so it sits better in the mix. I might be way off base, forgive me if I am.
Overall the sound of the entire kit does not represent a good jazz kit to me. I really like the intro drum part and the sound of the kit really suits that.....but less so when the full band is going. Again this is just my taste here...ignore me.
As mentioned the hi-hat needs help. It should be crisper and more present.....whatever it takes....perhaps less reverb on it....anything so it is a bit more up front in the mix. This is where the listener will latch on to the groove. That "and" of every 1/8th note beat needs to really cut.
There are some cymbal decays that end abruptly...one stuck out, a crash at :48 and then a fast sticked cymbal part at 2:34.The sound of the ride cymbal bugs me a little......I prefer a ride that has a nice thin crisp sound and perhaps even a sizzle in this case. It has a little too much bell sound for me as if it were a small cymbal. I like those big rides so I really hear those "tings" off the stick tips, real nice and separated and sitting in a space where they are not fighting anything else.
To me if you lose the boom in the bass, drop it back in the mix, change that hat sound and bring it up....and see what you can do to calm that ride down.....it will be a killer little track. As someone suggested...maybe look at the reverb. I gather MIR is a convolution reverb.....if it is new to new are you perhaps overusing it or could you re-evaluate what sort of space you want to use?
Just thoughts here, I doubt I could even do 1/2 way as well as you have. All I know is what I like to hear after 40 and more years or so of listening to music.
Again, I really like the overall song, nice writing. I like the harmonies. I am sorry if I went too far with my suggestions....just stating my opinions and the track to me is real close...the writing is solid, nothing needed there, just some small EQ and mix things and you are home.
What library did you use BTW or if individual VI's which ones, drums, bass etc?
Pro Tools 10 w/CPTK| Eleven Rack| Sibelius6|Spectrasonics- Omnisphere, Trilian,StylusRMX| Kontakt 5| Garritan-Instant Orchestra,J&BB3,GPO4| Sibelius 6| Reason4| Drumcore3| Toontrack-EZ Drummer,Superior Drummer,Drumtracker,EZ Keys| Izotope- RX2, Ozone 5, Iris| EWQL PLAY -Silk, RA, Gypsy, Fab Four, Voices Of Passion, Symphonic Choirs, StormDrum 2, Symphonic Orchestra Plat.|Project Sam-Symphobia| 2.66 MacProQuad 8GB ram 10.6.8, 2.4 MacBook Pro Intel Core 2 Duo 4GB ram 10.7.5