Jacksonville Beach-based singer and guitarist Landon Gay is a true saltwater cowboy. And therein may lie secret to the unique Americana sauce he’s injected into the four singles he’s released under the moniker Howdy, which have collectively racked up more than three-quarters-of-a-million plays on Spotify. Indeed, embedded in Howdy’s lofi, minimalist ballads is a palpable authenticity — in the pace …