The Paul Keller Orchestra has long had a tradition of a regular weekly Monday night big-band gig, in several different locations including the Firefly Club and Keystone Underground. With the shuttering of Keystone late last year, the band was without a home — temporarily. But Paul Keller recently announced a new Monday night residency at the Zal Gaz Grotto Club, 2070 W. Stadium Blvd. in Ann Arbor.