Dear Drago,
I agree with/love the idea of a "Jazz Band" collection of skins featuring Bard as a Saxaphone player although I confess I could also see Bard playing the trumpet and paying homage to greats like Armstrong, Chet Baker and Don Alias. With that said I feel there are other, better choices to fill the other roles and I'll go over my what I'd like to see.
Percussionist, Shaco, 1350 or 1820 RP:
1: Shaco's knives would become drumstix.
2: Shaco's "Jack in the box" traps would become drums that would fire musical notes or soundwaves as the Jack bangs the drums.
3: Shaco's 2 Shiv Poison active would make the "ringing crash" sound produced by symbols upon impact. This same sound would be used whenever Shaco exited stealth.
4: His clone's death animation would shower drumstix in multiple directions.
5: His physical features and other notable features would pay homage to the late Tony Williams or other deceased Jazz musician(s) with a dress-shirt, long tie and slacks.
6: Would fill the team's Jungling role.
7: Alternatively I could also see Percussionist role being filled by Draven, Heimerdinger or Akali with similar effects ( drum role while Akali is in her smoke screen or a drumbeat every time Draven hits somebody with his Q and the symbols chiming upon kills ).
Bassist, Leona, 750-975 RP:
1: Appearance would pay homage to Vivien Garry.
2: Shield would be a cello.
3: Abilities would envelope foes in sound with different musical combinations for each ability.
4: Would fill the team's position of top-laner ( I promise, she is still viable top )
5: Could also see Bassist role being filled by Singed, Jarvan or Nautilus.
Vocalist, Karma, 975-1350 RP:
1: Karma, having a naturally dark skin color, is a natural choice to pay homage to many now deceased African-American-female jazz vocalists.
2: Karma would sing her naturally spoken lines.
3: would fill the team's magician-based role.
4: I really can't see another clear choice for a vocalist who has the same potential to pay the same sum of respect.
Trombone, Caitlyn or Twitch, 975-1350 RP:
1: Projectiles would be musical notes.
2: Piltover Peacemaker or Venom Cask ( her Q or his W ) would make the sound of the slide being pushed out.
3: Firing her 50. Cal Net or Contaminate would make the sound of the slide being pulled in.
4: Using their ults would queue a bit of jazz that played while the ult is active.
Secret event:
Having all five dance, joke or taunt at the same time would cause them to play "When the Saints go marching in" which could be heard globally.
The above was simply off the top of my head. As much as I like the idea I don't know enough about programming or whatever other knowledge I need to put together a skin series.
Thanks for sharing your wonderful idea; I'm hoping for a set jazz skins thanks to you,
Mr. Beane.