(HUDSON, N.Y.) – Folk-pop sister group SHEL shares a double-bill with acoustic grunge-rock singer-songwriter Otan Vargas at Club Helsinki Hudson on Friday, April 3, at 9pm. Appealing to fans of Sarah McLachlan, Nickel Creek and Regina Spektor alike, SHEL gets its name from the four sisters who comprise the group: Sarah (violin, bass), Hannah (piano,…