A written musical score fixes two things with reasonable precision: pitch, which specific note to play, and rhythm, exactly when and for how long to play it. It leaves considerably more room for a performer's own interpretive choice in two other dimensions: dynamics, how loud or soft a note or phrase is played, and articulation, how a note is actually attacked, sustained and connected to the notes around it. The same fixed pitch and rhythm, performed with different dynamic and articulation choices, can end up communicating genuinely different musical statements, even though the notes on the page never actually change.
Dynamics shape a phrase's emotional weight and forward motion
Dynamics govern a note or passage's relative loudness, ranging from very soft to very loud, and composers typically indicate a general dynamic level or a gradual change in dynamics using specific notational markings, though the precise, moment-to-moment shaping of dynamics within those broader markings is still substantially left to a performer's own musical judgement. A phrase performed at a single, unvarying dynamic level tends to read as comparatively flat and static, while the same phrase performed with a carefully shaped dynamic arc, swelling toward a peak and receding afterward, can communicate a real, felt sense of emotional build and release that the identical notes, performed without that dynamic shaping, simply don't convey on their own.
Articulation determines how connected or separated each note feels
Articulation governs how a given note is actually attacked and how it connects, or doesn't connect, to the note that follows it — a smooth, connected articulation called legato, in which successive notes flow into each other with no audible gap or separation, produces a fundamentally different musical character than a short, detached articulation called staccato, in which each note is deliberately separated from its neighbours by a distinct silence, even when both articulations are applied to the exact same underlying sequence of pitches and rhythms. A melody performed legato tends to read as smooth, lyrical and connected, while the identical melody performed staccato instead reads as light, pointed or energetic — a difference in perceived musical character produced entirely by articulation choice, with the underlying pitches and rhythm never actually changing between the two performances.
What we're still unsure about
The basic definitions of dynamics and articulation, and their genuine, demonstrable impact on a performance's musical character, are well established in music theory and performance pedagogy. What's more a matter of ongoing interpretive and stylistic debate is exactly how much a performer should exercise personal dynamic and articulation choice beyond what a score's own explicit markings specify, particularly for historical repertoire whose composer left comparatively sparse markings by later standards — performers, teachers and musicologists continue to debate how much of a given historical piece's dynamic and articulation shaping should be treated as historically informed convention versus genuinely open to a modern performer's own individual interpretive choice, a live question in performance practice rather than one with a single agreed answer.
This sits inside Dynamics, Articulation & Expression, one of seven topics in Performance, one of four domains in Music, one of seventeen subjects the app can quiz you on.