What are five formal elements in George Gershwin's song "Summertime"?

"Summertime" is a 1934 aria composed by American composer and pianist George Gershwin. Gershwin composed the song for his 1935 English-language opera, Porgy and Bess, while the lyrics were written by his younger brother Ira Gershwin and American writer DuBose Heyward. In fact, Gershwin's opera is based on Heyward's most popular novel, titled Porgy (1925).
1. Structure and Setting
"Summertime" has two verses, and the text is syllabic (one note pre-syllable). Gershwin masterfully blends several musical genres, making the song easily adaptable to different styles. Thus, following its production, "Summertime" has been recorded numerous times by various artists—such as Billie Holliday, Sam Cooke, Ella Fitzgerald, and Janis Joplin. Gershwin did, however, receive some criticism for the lyrics, as some considered them racist and offensive to black people:

Summertime, an' the livin' is easyFish are jumpin' an' the cotton is high.Oh, yo' daddy's rich and yo' ma is good-lookin'So hush, little baby, don' you cry.
One of these mornin's you goin' to rise up singin'Then you'll spread yo' wings an' you'll take the sky.But till that mornin', there's a nothin' can harm youWith Daddy an' Mammy standin' by.

2. Melody
Melody could be considered the most important element of a song. A melody is made up of various pitches and notes which form a specific shape or pattern. Although it sounds pentatonic at first, the melody in "Summertime" is actually based on a six-note scale. It is a mixture that includes elements of jazz, blues, operatic and orchestral forms, and African American folk music of the nineteenth and twentieth centuries. The texture of the melody is homophonic, with some examples of heterophony.
3. Harmony
The most common elements used to harmonize a melody are chords and triads, which are, essentially, vertically combined pitches in groups of three notes. "Summertime" has a strong triadic harmony, which is characteristic of jazz and blues. In the first verse, a harmonic ostinato (repetitive motif) is established, which is typical of lullabies. This is why many consider "Summertime" a lullaby as well.
4. Key
When pitches are categorized into groups they form a key. All of the notes within a specific key usually come from a certain scale. The most common keys are major and minor. In "Summertime" the key is in the scale B minor.
5. Rhythm
Rhythm describes the way time is applied to a piece of music. All of the notes in the melody have a different length and thus have rhythm. In "Summertime" the rhythm resembles a beat, which has often been described as slow and occasionally syncopated. The tempo is slow, and sometimes the meter can't be heard or felt.