Pittsburgh-based guitarrorist Aaron Myers-Brooks summons up precision-lined metal shredding and keyboard-thrusted polyrhythms on his excellent, new one-man/one-song instrumental single, “Multilinear Smattering,” out last week on Bandcamp. Now, the entire “single” runs less than two minutes but, that, for a descendent of Orthrelm, is more than enough time to make a hell of a racket. Myers-Brooks,…