by Richard S. Ginell Not many will bother to recall that Clark Terry was the first trumpeter to make a recording with Selmer's Varitone attachment -- an electronic hookup to an amplifier that allowed a horn player to play octaves. Though the instrument quickly fell out of favor after a very brief vogue, it still produced an attractively soulful sound that was a good fit with Terry's jaunty, slurry, note-bending manner. Naturally, there is yet another ride on the "Mumbles" train called "Electric Mumbles," in which Terry talks back and forth to his horn, and he sings, scats and mumbles a few choruses of "Take the 'A' Train." But he also plays some mighty soul-satisfying blues on his electric horn on "Take Me Back to Elkhart" (Selmer's headquarters), really exploiting the opened-up lower register. The rhythm section (Don Friedman, piano; George Duvivier, bass; Dave Bailey, drums) plays straight and solid jazz behind their happy-go-lucky tinkerer/leader; there is nothing unmusically sensational about anything that happens here.