Many artists cover standards by Gershwin, Monk or Ellington, but very few can really dig in and mine the emotional nuance of these historic pieces. On Bolivian Blues Bar (Narada 70876-13280-2-8; 48:52) Alex de Grassi does the masters proud, with original and beautiful solo arrangements in the raw, inspired by the work of vocalists Ella Fitzgerald, Billie Holiday and more. The guitarist gives a detailed, original read to every piece, anchored in the revealing emotion of a singer’s perspective. The results vary from a spindly dark, bluesy twist on “It Ain’t Necessarily So,” with de Grassi delivering harmonic hammers and bassy undertones to a driving, percussive punctuation mark on “Little Rootie Tootie.” De Grassi’s work can be stirringly romantic (the intricate harmonies and stirring blocky chords on “You Go to My Head”) or almost wickedly humorous (a bouncing “Woody Woodpecker Theme” is touched with darker-toned harmony to make an interesting statement). He uses the entire instrument to convey the shadings of a complex piece. On “‘Round Midnight,” for example, the guitarist takes his time to reveal mixed emotions, backing a stark, notey melody with subtle, irregular chordings to build tension, regret and even hope.