Change Timbre by Adjusting Picking-Hand Position
Timbre is most typically expressed on the guitar by the position of the picking hand in relationship to the bridge and soundhole. Playing toward the fingerboard side of the soundhole emphasizes the fundamental tone and yields a warmer, darker sound called sul tasto (Italian for “below the fret”). Playing toward the bridge emphasizes the attack and higher overtones, yielding a edgier, steelier, and brighter sound known as either ponticello (Italian for the bridge of a musical instrument) or metalico (Spanish for metallic). Working between these two poles allows the player to accentuate and contrast individual notes and phrases.
Play the arpeggios in Example 1 and gradually move your hand from sul tasto position (near the fingerboard) in measure 1 down to metalico position (near the bridge) as you approach measure 4. Repeat the phrase and reverse the movement—moving from metalico to sul tasto. Listen to how the gradual change in timbre adds a sense of movement to what is otherwise a fairly repetitive phrase. The change in timbre also directs more attention to the one accented note in each measure—that note moves back and forth between F# and E, but it sounds different each time. Play those notes alone, rearranged in measures 5 and 6, and listen to the movement as the hand travels from sul tasto to ponticello.
Excerpted from The Alex de Grassi Fingerstyle Guitar Method