Seeking a definition

Pitch is determined by a sound’s frequency. Notes that sit in different positions on a musical scale, called tones, have different pitches. Modern Western music, for example, combines 12 tones, with the A at the middle of a piano keyboard having a frequency of 440 hertz. Other cultures work with fewer tones. The first few notes of “Twinkle, Twinkle, Little Star” vary only in pitch.

Click here to hear a middle A and here for the 12 tones used in Western music.

Rhythm emerges because different notes can last for varying amounts of time. Notes with different durations are represented differently in written music: Some have little flags, dots or open circles. A quarter note, for example, is drawn as a closed circle with a vertical line; it lasts for one beat. The notes of the Beach Boys’ “Barbara Ann” and “One Note Samba” vary only in note duration.

Click to hear whole notes, half notes and quarter notes. Click here to listen to “One Note Samba.”

Combining different pitches and rhythms allows for the creation of melodies, the same way the combination of words makes a sentence. And when different notes are played at the same time to create chords, rather than just successively, they can lead to harmony. Other factors mix in to affect the character of the piece. Dynamics, how loud each note is and how that loudness changes over the course of several notes, opens even more room for variation. And timbre, or tonal quality, distinguishes one instrument from another — a piano sounds different from a tuba, and Celine Dion sounds different from Macy Gray. Tempo characterizes the overall speed of a piece. Changing multiple factors at a time leads to endless musical possibilities, from “Für Elise” to “La Bamba.”

Click to hear a guitar, piano and string instrument all playing “Für Elise.”

Considering beauty
While some would argue that any variation of sound with the above features makes music, others say music is more than the sum of its parts. Perhaps sound has to be pleasing to qualify? Pythagoras, an ancient Greek philosopher, recognized that when notes with pitches forming simple ratios are played together, they sound pleasant. Using a single string with a movable bridge — which allowed him to pluck two notes at once — he found that when one side of the string was half the length of the other, it created two notes that sound lovely together. (In Western music today, if a string producing the note A at 440 hertz is halved, it creates another A an octave higher.) A pleasing blend also occurred when one side was two-thirds or three-fourths the length of the other. Using these ratios, Pythagoras built a seven-note scale, and his ideas still help musicians understand why some music sings and other tunes fall flat.

Click here for more on Pythagoras’ scale, including audio clips.

Elizabeth Quill is former executive editor of Science News. She's now a freelance editor based in Washington, D.C.