If you are new to classical music, these are some terms to understand before continuing:
Key, measure (or bars), phrase, period, form, style, and some others. There are (or will be) posts discussing each of these.
Most of my posts will be about symphonies since they’re my favorite style,
The foundation of a symphony orchestra’s repertoire is the symphony. No matter the size of the orchestra, its prestige, or its budget, every symphony orchestra performs at least one symphony per season. Actually, it is more remarkable when an orchestra doesn’t perform a symphony.
So, what’s a symphony?
There may be some confusion about this word. A symphony can mean a work of musical art or it could mean the ensemble that performs it. The full term for the ensemble is a symphony orchestra and sometimes a philharmonic orchestra.
So what is a philharmonic orchestra? Today, when a symphony or orchestra (both are used to describe the ensemble) has a full complement of musicians (minus any singers. Singers are generally not a part of a symphony orchestra’s or philharmonic’s personnel), the terms are synonymous with philharmonic orchestra. Historically, the difference will be in financing. There is such a thing as a chamber orchestra which is different from a symphony orchestra or philharmonic orchestra. A chamber orchestra is comprised of a smaller group of musicians and the instrumentation (the kinds of instruments used) can be customized either by the composer who may want a smaller size.
One last note about ensemble names: Early jazz ensembles often used the word “orchestra” to indicate high class. “Paul Whiteman and His Orchestra”, “Benny Goodman and His Orchestra”, and the list goes on. In addition, “orchestra” also implies a larger size than the previous generation’s Dixieland quintet or sextet (an ensemble of five or six).
A typical instrumentation for a symphony orchestra would be 2 flutes, 2 oboes, 2 clarinets, 2 bassoons, 4 French horns, 2 trumpets, and 2 timpani (not two performers. Two kettledrums), 6 to 10 1st violins, 6 to 10 2nd violins, 4 to 8 violas, 8 to 10 cellos, 4 basses (actual numbers may vary. Consult your local symphony orchestra about their personnel). Beginning in the Romantic period (around 1800, depending on who you ask), composers often added more instruments.
For his great 9th symphony (1822-24), Beethoven adds a piccolo, contrabassoon, vocal quartet (soprano, alto, tenor, and baritone), full choir, triangle, crash cymbal, bass drum, 2 trombones, and bass trombone.
Felix Mendelssohn’s “Scottish” Symphony (no. 3, 1829-42) uses the common instrumentation of 2 flutes, 2 oboes, 2 clarinets, 2 bassoons, 4 French horns, 2 trumpets, and 2 timpani.
In his Grande messe des morts (Requiem Mass (1837) – this is not a symphony, but it uses a symphony plus a bunch of other instruments), Hector Berlioz uses 4 flutes, 2 oboes, 2 English horns, 4 clarinets, 8 bassoons, 12 French horns (yes, 12!), 4 cornets, 4 tubas (yes, 4 tubas!), 16 timpani (10 players), 10 pairs of cymbals, 2 bass drums, 4 tam-tams, 25 1st violins, 25 2nd violins, 20 violas, 20 cellos, 18 basses, vocal solo, chorus (80 female voices, 60 tenors, 70 basses), brass choir 1 (4 trumpets, 4 trombones, and 2 tubas), brass choir 2 (4 trumpets and 4 trombones), brass choir 3 (4 trumpets and 4 trombones), brass choir 4 (4 trumpets, 4 trombones, and 4 ophicleides (or tubas, if you can’t find ophicleidists)).
Robert Schumann’s 4th Symphony (1841 or 1851, depending on which version you’re looking at) uses the typical orchestra, but adds 3 trombones.
Johannes Brahms’ 4th Symphony (1884-85) adds a piccolo, contrabassoon, 3 trombones, triangle, timpani, and strings.
Tchaikovsky’s Symphony No. 6 “Pathetique” (1893) has 3 flutes (1 of those doubles on piccolo), 2 oboes, 2 clariets, 2 bassoons, 4 French horns, 2 trumpets, 3 trombones, 1 tuba, 1 timpanist, 1 bass drum, 1 pair of cymbals, 1 tam-tam, and a string section that is typically 8-10 1st violins, 8-10 2nd violins, 68-violas, 8-10 cellos, and 4-6 basses.
The instrumentation for Gustav Mahler’s 8th Symphony (“Symphony of a Thousand”, 1906) is almost as crazy as Berlioz’ for his Mass: 2 piccolos, 4 flutes, 4 oboes, English horn, 3 clarinets, 1 Eb clarinet (a smaller version), 1 bass clarinet, 4 bassoons, 1 contrabassoon, 8 French horns, 8 trumpets (4 are offstage), 8 trombones (3 are offstage), 1 tuba, 4 timpani (played by one person), bass drum, triangle, cymbals, tam-tam, 2 tuned bells, glockenspiel, organ, celesta, piano, harmonium, 2 mandolins, 2 to 4 harps, 20 1st violins, 20 2nd violins, 16 violas, 20 cellos, 12 basses, (pause for a breath). The singers: 3 soprano soloists, 2 alto soloists, 1 tenor, 1 baritone, 1 bass, 2 full SATB choirs, and children’s choir. A reputable choir might have between 100 and 150 singers. A typical children’s choir might have between 20 and 50 singers.
More recently, Henryk Gorecki’s Symphony No. 3 (1976 and, yes, I know that 1976 isn’t that recent) uses a 4 flutes, 4 clarinets, 2 bassoons, 2 contrabassoons, 4 French horns, 4 trombones, 1 harp, 1 piano, strings, and a soprano soloist.
Summary of size: It depends on the composer and the situation. Mendelssohn typically kept to the standard with little deviation. Late Romantic composers such as Mahler want a gigantic sound. Beethoven didn’t give a shit; he wanted what he wanted. Berlioz wanted to see what he could get away with.
In short, a symphony is a composition that generally has four movements.
Fine. What’s a movement?
A movement within a symphony can be heard by itself in a concert or over the radio. In other words, it can be heard as a complete composition. But it’s not. The composer creates each movement individually so that each is complete in form and mood.
The symphonies of Beethoven (except the 6th which has 5 movements), Brahms, Mendelssohn, Schumann, Tchaikovsky and many others have four movements. Mahler’s Symphony No. 8 has 2 movements. Gorecki’s Symphony No. 3 has 3 movements.
Form is what binds the movement together. The lay listener doesn’t need to understand musical form to appreciate a performance, but understanding it helps. In short, form is how the composer organizes and manipulates his or her themes. You can think of a theme as a tune that can stick in your head or that you can whistle to.
What forms are there?
Instead of listing all the kinds of forms out there, I’ll list the most common forms you’d find in a symphony. For the first movement, you will almost always find sonata form. The second movement is often a theme and variations. The third movement is often a minuet and trio. The final movement is often in sonata form or theme and variations.
What are these forms?
I think these will be good individual post topics.
 For more information, you may go to http://www.differencebetween.net/language/words-language/difference-between-philharmonic-and-symphony-orchestra/ or https://www.ludwig-van.com/toronto/2014/08/04/classical-101-the-difference-between-chamber-philharmonic-and-symphony-orchestra/ or do a google search on your own.
 Quick math: 430 musicians. Questions to ponder: 1) Who’s going to pay for all this? 2) Is the hall big enough to hold this many musicians?
 Quick math: Mahler’s “Symphony of a Thousand” can have as many as 500+ musicians, but the subtitle is better than “Symphony of Half a Thousand”.