When Domenic Marte and the rest of his Latin music band takes the Harley-Davidson Roadhouse stage Sunday night at 7:30, the crowd will be expecting strong, musically complex, catchy pop-infused bachata music (a particular brand of romantic Latin music that originated in the Dominican Republic and spread from there). There's one thing they might not be expecting however: Clay Steininger, the group's guitar-slinging "gringo."