Pat Mallinger has grown into a wonderful saxist in the last several years, but many listeners already know that from his weekly wee-hours gigs with the Sabertooth Organ Quartet at the Green Mill. So the surprise this weekend will likely be Bill Carrothers, the best underappreciated pianist in jazz today. Living on Michigan's Upper Peninsula gives him a relatively low profile, but he's got a strong and engrossing approach: a magisterial mix of gauzy sentiment and bold, blunt phrasing, plus an ability to adjust to a variety of contexts. Two weeks ago at the Jazz Showcase, spearheading the rhythm section for freewheeling tenor saxist Dewey Redman, he all but commandeered the set with solos of ferocious counterpoint and keyboard-spanning extended harmonies. That performance was quite a switch from the stately, brilliantly colored work on his double-CD concept album, Armistice 1918 (released last year on the French label Sketch but available online through Carrothers's own Bridge Boy label). Lavishly packaged with photos and liner notes, it's an Ivesian reflection of his ongoing interest in history, mostly comprising WWI-era tunes that turn nostalgic, revisionist, or deeply introspective under his direction. Like most of Carrothers's discs, it features sparkling drummer Bill Stewart, and in fact Carrothers has received the widest recognition in the U.S. for his appearances on Stewart's Blue Note recordings. But he's gained a large and loyal following in Europe as a leader--especially in France, where his discs have regularly won awards and appeared on top-ten lists. Do not miss him. See also Saturday. Fri 6/24, 9 PM, Green Mill, 4802 N. Broadway, 773-878-5552, $10.