A strain is a series of musical phrases that create a distinct melody

Melody

A melody , also tune, voice, or line, is a linear succession of musical tones which is perceived as a single entity...

 of a piece

Musical composition

Musical composition can refer to an original piece of music, the structure of a musical piece, or the process of creating a new piece of music. People who practice composition are called composers.- Musical compositions :...

. A strain is often referred to as a "section" of a musical piece. Often, a strain is repeated for the sake of instilling the melody clearly. This is so in ragtime

Ragtime

Ragtime is an original musical genre which enjoyed its peak popularity between 1897 and 1918. Its main characteristic trait is its syncopated, or "ragged," rhythm. It began as dance music in the red-light districts of American cities such as St. Louis and New Orleans years before being published...

 and marches

March (music)

A march, as a musical genre, is a piece of music with a strong regular rhythm which in origin was expressly written for marching to and most frequently performed by a military band. In mood, marches range from the moving death march in Wagner's Götterdämmerung to the brisk military marches of John...

.

In the House M.D. episode Simple Explanation (Season 5), House is heard saying "You deduced that by removing your sunglasses to the strains of a Who

The Who

The Who are an English rock band formed in 1964 by Roger Daltrey , Pete Townshend , John Entwistle and Keith Moon . They became known for energetic live performances which often included instrument destruction...

 song?" The quote itself is a reference to a common plot device in CSI: Miami

CSI: Miami

CSI: Miami is an American police procedural television series, which premiered on September 23, 2002 on CBS. The series is a spin-off of CSI: Crime Scene Investigation....

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