Tetrad Upholstery Vivaldi Loose Cover Sofa at Kings of Nottingham for that better deal. Click below to buy online or call to order over the phone on 0115 9258347. Tetrad Upholstery Vivaldi. Available in two sizes of sofa, a high back wing chair and footstool, the Vivaldi tailored loose cover collection, in both washable and dry cleanable covers. Couple the ranges versatility with its casual scatter back, and you have simply unrivalled comfort.