Confident, tight, and finessed, its songs spangling with a sheen of shimmering synths, Spoon showed off sterling professional skills and experimental prowess at The Arlington Theatre on January 18. Colorfully atmospheric songs such as “Can I Sit Next to You,” with its snake-charming string section, and the moody “I Ain’t the One,” propelled by drummer Jim Eno’s rib-rattling pounds, stood their own along more traditional hits such as “Do You.” At points, Spoon’s relentless perfectionism read as an arena-show distance, and the well-oiled band, good as it was, felt emotionally mechanical. But that’s the price of being a consistently good act; and if all the dancing were any clue, its recipe is working.