Now a quartet, Swiss pianist Nik Bartsch’s Ronin’s remains undiminished in its rhythmic focus

After Ronin, the long-running band of Swiss pianist and composer Nik Bartsch, dropped its 2010 studio album, Llyria (ECM), the group experienced some major personnel shifts. In 2011 six-string bassist Björn Meyer left the group and was replaced by Thomy Jordi, who plays a conventional four-string model.…