Conclusion

Tango and Salsa are both well known as partner dances from Spanish-speaking countries. When we look at pieces of both genres, we see a huge difference between the musical aspect of the dances. However in these two pieces, they are both written in canon chordal structures, they both have thick textures, extensive string parts, solos, contrasting tempos, several themes, time signatures, and they both having a very moving forward theme in them. From looking at the musical aspects of Piazzolla's Invierno Porteno and Gershwin's Overtura Cubana, we can find the similarities between the genres of Tango and Salsa.

Chord Structures

To further compare the two pieces, we should look at some of the chord structures of them. Both the Tango and the Salsa are canons, which means one voice repeats another at different times throughout a piece using the same chords over and over again. 

At the end of Piazzolla's Tango, the chord structure is the following:

I V vi ii V I  IV V

(using roman numerals, and the lower-case letters represent minor keys)

Tone Colour

 Tone colour, also known as timbre, is a term that describes the quality of sound in music. Timbre is what makes a particular musical sound different from another, even when they have the same pitch and loudness. For instance, it is the difference between a guitar and a piano playing the same note at the same loudness. Both pieces have string instruments, (cellos, violins and a bass) but Gershwin's Overture has a full orchestra with wind and brass instruments, which gives it a different tone colour. There are more instruments in Gershwin's piece, while Piazzolla's is just a trio. Therefore, Gershwin's piece has a thicker and richer tone than Piazzolla's. 

Structures

Before we analyze the structures of the two pieces,  we should first analyze what the structure of a piece of music even is. A songs structure is how it's organized. An example of the structure of a song is intro - verse -hook - chorus - verse - hook- chorus -bridge - chorus -coda. (this is the structure of most popular music today). To further analyze what a song structures are, these are the definitions of the parts of the structures:

Chorus: The chorus is a lyric-music combination that is repeated with little or no change throughout the song. Usually, the chorus lyrics include the song title and gives the listener a general idea about the song topic. The chorus music includes the most catchy melody in the song...The chorus is generally the part that your listener will remember from your song.

Verse: The verse has the second melody of the song, this melody hardly changes throughout the song. What changes is actually the verse lyrics; as the verses usually give details about the song topic.

Bridge: The third melody and the one that is -in most song structures- appearing only once. It is better if the listener gets a "tiny" surprise in the bridge; that can be a change in the chord structure accompanied by a smooth shift to another scale...etc. However, the bridge melody always ends by shifting back to the original mood and repeating the chorus all over again. As for the bridge's lyrics they usually represent a conclusion or a flash back to the whole song, this adds to the surprise. 

Coda: The outro of a song- the ending.

The structure of Gershwin's Overture is ternary form. Ternary form is a three-part music form-usually schematized as A-B-A. What this means is the first and third part (the A's) are musically identical, and if not very similar. The B section provides a contrast from the two A sections. The B section is generally in a contrasting, but closely related key, usually the dominant key of the first section's tonic (a perfect fifth above) or the relative or parallel minor or major, less often the sub-dominant key (a perfect fifth below).

The first part (moderato e molto ritmato) is preceded by a (forte) introduction featuring some of the thematic material. Then comes a three-part contrapuntal episode leading to a second theme. This first part finishes with a recurrence of the first theme combined with fragments of the second.

A solo clarinet cadenza leads to a middle part, which is in a plaintive mood. It is a gradually developing canon in a polytonal (which means  several tones together) manner. This part concludes with a climax based on an ostinato of the theme in the canon, after which a sudden change in tempo brings us back to the rumba dance rhythms.

The finale is a development of the preceding material in a stretto-like manner. This leads us back once again to the main theme.

The conclusion of the work is a coda featuring the Cuban instruments of percussion.

The form for Piazzolla's Invierno Porteno is not in a certain form. This is the structure of the Tango from beginning to end:

Slow intro Theme A (minor key)
Fast - theme A’
Transition
Slow tempo- Theme B
Fast Tempo- New Material (pentatonic –open 5ths) Theme C
Slow tempo (cello) Theme D
Theme D passed to violin
Fast Tempo Theme D’
E theme passed to piano
Slow Theme D
Slow theme new material “E” –passed from strings to piano.

The form of Piazzolla' piece is built among the tempos of the piece. All Tangos follow the pattern of a slow intro, then the tempo speeds up and the pattern continues until the slow outro. The slow tempo sections are in 3/4 time, while the faster tempos are in 4/4 time. (the 4/4 time signature gives it more of a moving forward pace). 

The Tango

TANGO….Just the word conjures up exciting images and inspires many 

associations and interpretations, such as passion, sensuality, drama, gender wars, even 

violent ones, a national identity, a by-gone era, and a universal art form.

 According to the Grove Dictionary and Oxford Music Online (subject heading "Tango"), a tango is a piece "in duple meter  with a characteristic rhythmic figure, it consists of two sections, the second usually in the dominant or relative minor." It gives the rhythmic figure as one of the following two possibilities:

1. Dotted eighth plus sixteenth, two eighth-notes
2. Sixteenth plus eighth plus sixteenth-note, two eighth-notes

The Harvard Dictionary of Music defines the tango as being a song in two equal repeating sections; the first section being in one key and the second being in either the key of the dominant or relative minor of the original key. This structure is very important to early and modern tango styles.

The musical element that really sets tango apart from other song types is syncopation. Most often seen written in 2/4, it is characterized by being in a duple meter (2/4 or 4/4 commonly). As Tango progresses throughout the musical time periods, the syncopation becomes more and more complex. However, simple repeating syncopated rhythms (8th-dotted, 16th, 8th, 8th) are very commonly heard.

Tango music is usually just associated with dancing, but there is also a common lyrical thread. The Harvard Dictionary of Music also says that originally the songs were often about urban or social issues, originating in urban areas of Argentina.

 It is traditionally played by a sextet, known as the orquesta típica, which includes two violins, piano, double bass, and two bandoneóns. Earlier forms of this ensemble sometimes included flute, clarinet and guitar. Tango may be purely instrumental or may include a vocalist.

All sources of Tango stress the influence of African communities and their rhythms, while the instruments and techniques brought in by European immigrants in the 20th century played a major role in its final definition.

The Tango usually features violins playing in the melody along with the Piano and Bandonean. The Tango can usually be improvised. There's always four beats to a bar and feature syncopated (off beat) rhythms (because it is a dance). Tangos are also always in a minor key and feature layers of ostinato. (repeated patterns)

There is no percussion section in the tango orchestra, but rhythmic patterns are

heard in different instrumental layers of the texture. The bass line often carries the

prominent dance rhythm, or perhaps it may be in an accompanying middle part such as

the bandoneón or the string section.