Every year, band and choral students in the middle and high schools around the country prepare pieces to be adjudicated in solo and ensemble competitions. As the students practice and prepare, they learn to play or sing the notes. They pay attention to production and tone quality, and proper concert deportment. They work on getting the tempo and mood right. They research to learn a little about the historical context of the piece. They listen to balance their part with the accompanist or other players. They practice enough to work through their nervousness to try to create a good performance.
As I have listened to many years of these adjudications, I have noticed that the students who are the most enjoyable to listen to and show the greatest promise as musicians are those who learn to give SHAPE to the musical phrases. A beginner might be so concerned with remembering the fingerings or counting the rhythms or conquering stage fright that they never reach the point of losing themselves in the music to give INTERPRETATION.
Composers try to give many indications in the score for how they intend the performer to interpret the music. They will mark the tempo at the top of the score with a metronome number (adagio 66, moderato 120, or allegro 144) and usually some comment about interpretation such as marcato (steady like a march) or dolce (sweetly) or con animato (with animated movement). They might mark a passage legato (smoothly connected) or staccato (detached). The scores will undoubtedly will include dynamic markings like "hairpins" crescendo and diminuendo (growing louder and then softer) or mf (medium loud) or pp (very soft). All of these markings will help the performer understand the mind of the composer, and yet there is room for the performer to bring the music to life through their own gifts.
Just like the dramatic, ever-changing waves on the ocean, a composition will demand finesse to bring out the subtle nuances of the musical phrases. The notes on the score are just squiggles of ink until they are brought to life by the performer. A gifted performer will look for opportunities to heighten excitement or build to a climax or broaden to the finish. They will know just when to soften or smooth out the tone to let the musical line breathe. Each phrase should have a SHAPE, a rise and fall, a most important stress, a beginning and an end. When a chorus sings each syllable with the same stress, the sound is lifeless and robotic. Most directors will try to get the singers to vary the way they sing the notes, especially repeated notes, so that there is forward motion and feeling in the phrase. Loud and soft singing is not enough, there should be more subtle variations in mood and stress.
Remember the waves of the ocean! Think of the motion, the color, the rise and fall, the changes in mood and tempo, then translate all this to your performance. No two waves are exactly the same. And though you may practice to become proficient and consistent, no two performances are exactly the same. That's what makes live performance so exciting! Remember to always give shape to the musical line!