This is a public answer to a Private Message just in case it is of interest to others too:

Jazz in Paris  (For Horace) -

Check these out first maybe, then look at the other places, especially around Les Halles...

Duc des Lombards. Rue des Lombards.
Sunset. Rue des Lombards.
Le Caveau de la Huchette. Rue de la Huchette.
Le Bilboquet. Rue Saint Benoit.
La Montana. Rue Saint Benoit.
Le New Morning. Rue des Petites Ecuries.
Le Petit Journal. Rue du Commandant Mouchotte.
Le Petit Opportune. Rue des Lavandieres-Ste-Opportune.
Slow Club. Rue de Rivoli.

Check local listings before leaving your hotel for who is playing.
Duc des Lombards, Le Petit Journal, & Le New Morning get big names.
Le Caveau, Le Biloquet, Le Montana, Slow Club, Le Petit Opportune & Sunset are clubby, friendly, & cool (in the old fashioned meaning of the word).

Have fun!

Miles.