Arranging and orchestration
ike in literature, about which somebody has said that the publication of a work meant for the author that he was relieved of correcting it permanently in his eagerness to polish it, with music happens the same thing. Save for the difference that, being a performance an individual matter, the composition may be played in a different way each time, according to its interpreter. A never-ending dissatisfaction and the search for perfection pushes the artist to intent to improve his own work or else's, according to his feeling or aesthetic approach.
The expression arrangement refers to what is done with what the composer wrote, and the term orchestration refers to which instruments are chosen to materialize this decision.
In classical music everything is already written, the composer specifies even the smallest details and the interpreter respects what is written. In popular music, instead, there is usually sheet music for piano, which means a melody line, with some elementary chords. For that reason, it is necessary to add form to it and musically polish what was written. It is necessary to make an arrangement.
If the player or the orchestra leader does not have the capacity to make it, they turn to a musician/arranger. The work of the latter, not only improves the piece according to his taste or inspiration, but many times is a necessity, because the score may otherwise result quite poor.
The arrangement admits some changes in the original melodies, in the chords of the harmonies, invents counter lines, connecting passages, writes solos for the instruments, embellishments, decides what is legato and staccato, creates variations, and designs the backgrounds to accompany the singers. In sum, it is a re-creation, an improvement of the primitive theme, but also can be a necessity due to the shortages of the original score, or to shape a style.
A good arranger can do this with neither distorting the melody, nor the spirit of the original. Nowadays we often hear classic tangos whose arrangements are so far-fetched that it is impossible to discover the melody.
Orchestration means to decide which instruments or voices will play the lines conceived in the arrangement. It is to decide if a specific part will be played by the bandoneons, or the violins or all together in an ensemble. If a passage had to be played in unison or as different lines. The aim of orchestration is, as well, to achieve the balance of the mass of instruments, a good design and the final shape of the musical piece.
It turns out evident that arrangement and orchestration are the keys that define the styles of the different interpreters. Each one lends to the composition a touch that makes it different. I think that without an arrangement a performance is impossible.
As for how influential an arranger can be, there are lot of examples. A very clear one was Osmar Maderna with the Miguel Caló Orchestra. He died and the orchestra continued with the same style.
Among the arrangers, without taking into consideration the great orchestra leaders that wrote their own arrangements, we can mention: Julio Ahumada, Enrique Alessio, Celso Amato, Héctor Artola, Alfredo Attadía, Emilio Balcarce, José Bragato, Víctor Buchino, Gabriel Clausi, Edelmiro D'Amario, Martín Darré, Eduardo Del Piano, Mario Demarco, Jorge Dragone, Nito Farace, Argentino Galván, Carlos García, Juan Carlos Howard, Armando Lacava, Carlos Lazzari, Horacio Malvicino, Pascual Mamone, Mario Maurano, Osvaldo Montes, Máximo Mori, Miguel Nijensohn, Roberto Pansera, Juan Polito, Osvaldo Requena, Tito Ribero, Aquiles Roggero, Julio Rosenberg, Ernesto Rossi, Fulvio Salamanca, Federico Scorticati, Ismael Spitalnik, Luis Stazo, Orlando Trípodi, among many others.