From 1750-1830, composers of the classical era experienced a degree of social developments when it came to being a working professional composer. Whilst during the Baroque era, most composers were contracted on a full-time basis by either the Church or private patrons, from about 1750, the prominence of the Church as the focal point in everyday society decreased. In addition, private patronage diminished so composers had to rely on a somewhat freelance work ethic.
Since the advancement of instrumental music was beginning to take shape, this was not a major problem for most composers. In addition, the expansion of tuition in musical instruments and composition also meant that many composers were able to make an income from the middle class daughters of high society, who deemed it fashionable to take music lessons.
Mozart himself found this particular struggle, when private patronage began to run dry and he turned to teaching, performing and composing to make ends meet. However, he died a poor man in huge debt. Life for a musician or composer in the classical era was a hard and often not financially rewarding. With the advancement of instrument manufacturing techniques, music of the Classical era leaned more towards music for instruments rather than a bias towards choral music. This is certainly evident when it came to the First Viennese School, a term coined by Raphael Georg Kiesewetter in 1834.
The three greats; Wolfgang Amadeus Mozart, Joseph Haydn and Ludwig van Beethoven are easily the main figureheads when it comes to the classical period. The three composers were actually piers and even perhaps colleagues; Mozart and Haydn were said to have performed in concerts together and Beethoven even took the odd lesson from Haydn. It is sometimes noted that Schubert was considered to be added to the First Viennese School but it has largely been discounted.
The Austrian capital city of Vienna was the epicentre of the classical period in music, and most composers and performers aimed to at least study or work in the city, although it was output of Mozart, Haydn and Beethoven which overshadowed so many other composers of the era. Whilst the Baroque era centred around choral music, especially church music, the classical period leaned towards instrumental music. The First Viennese School are all best known for their contributions to instrumental music, with Mozart perhaps being noted for his choral works also. Haydn himself wrote over 100 symphonies for the orchestra and all three composers wrote many sonatas and concertos for individual instruments, the vast majority being for the pianoforte.
It should be noted that the inclusion of Beethoven is somewhat contested, since Beethoven is considered a late classical into early romantic composer. All three composers had a huge impact on the development of western music during the classical era and they are considered to be amongst the greatest composers to have lived.