Fans of Stevie Nicks and Warren Zevon are familiar with acclaimed session guitarist Waddy Wachtel. His distinctly wiry riffs appear throughout their catalogs, including smashes like the former’s “Edge of Seventeen” and the latter’s “Werewolves of London.” Wachtel has tailored his style as needed: Whereas his playing turns gritty for folk rocker Melissa Etheridge, with singer/songwriter Jackson Browne he fills in the spaces with tone and melody.