LA - The solfége syllable for the sixth note of the major scale.
LARGHETTO - Slower than largo.
LARGO - Very slow.
LEADING TONE - The seventh degree of the major or minor scale "leading" up to tonic.
LEDGER LINES - Short lines that extend the staff up and down for pitches beyond the range of the five line staff.
LEGATO - Smooth and connected.
LEGGIERO - Light; delicate.
LENTO - Slow. Faster than largo, though slower than Adagio.
LOCO - Perform the notes as written. Typically used to cancel a notation indicating that the music be played an octave higher.
LYRE - An ancient harp-like string instrument. The player makes a sound by strumming it with a pick like a guitar, rather than plucking it like a harp.