Knowledge is Power
Una corda - Soft pedal.
Variation - The manipulation of a theme by the use of melodic, rhythmic, and harmonic changes.
Whole note/rest - A note/rest equal to two half notes and four quarter notes.
Accelerando, accel - Gradually faster.
Balance - The harmonious adjustment of volume and timbre between instruments or voices; it can be between players or vocalists or electronically while recording or mixing.