[Whoops, you may have noticed that my history has a hole in it. We jumped from the 14th to the 17th quite without explanation. sorry, got a little ahead of myself. The following should have been inserted before the stuff about the continuo.]
Not until the end of the 16th century would we see the true orchestra in formation when Giovanni Gabrieli (1557-1612), the organist and choirmaster at St. Marks, Venice began composing pieces where voices and instruments would contrast one another to achieve a striking polyphony. He utilized two choirs, four soloists, an organ and sections of violas, cornets and trombones in his motet
In Ecclesi (1608):
Giovanni Gabrieli - In ecclesiis (1608) - YouTube
In his piece,
Sonata pian’e forte (1597), Gabrieli uses two sections, one of cornett with three trombones and another of viola with three trombones that not only contrast beautifully but when one section plays by itself, the music is soft; when both sections play, the music becomes loud (hence the title). The contrast isn’t simply between lines of harmony but also in dynamics. In the clip below, the instruments are updated in the spirit of what Gabrieli was aiming for (this piece is often played by high school bands):
Giovanni Gabrieli Sacra Symphonia Sonata Pian'e Forte - YouTube
What set Gabrieli’s attempts apart from earlier church music was that he was aiming to make music suitable for public listening rather than as a purely functional thing such as for church services or for dancing. Gabrieli sought to make the music itself the center of attraction where people could attend just to listen and enjoy. Gabrieli was successful in that he garnered audiences of aristocrats to attend these performances. By the later half of the 17th century, the common people were also attended these concerts.
By 1620, secular music was being performed publicly in Lübeck, Germany after Evensong (a.k.a. vespers or evening prayer). Since this happened towards evening, it was known Abendmusik. During the English Civil War (1642-1651), musicians began to put on concerts in taverns in and around London for those willing to pay a small fee to attend.
Around this time, opera came to be and became very popular among both the wealthy and the masses. The first opera house opened in Vienna in 1637. By 1650, Vienna had four opera houses operating simultaneously. It was through opera that the modern orchestra began to form. The reason is that the voices required instrumental support and had to convey the correct emotions. The composers began to assign different groups of instruments to convey various moods—strings, horns, winds, percussion—and so we see the beginnings of the symphony orchestra here. And because opera spread so rapidly across Europe, there was a need to standardize the instrumental lineup so that any orchestra could perform it anywhere. In fact, the word “orchestra” came from opera. The Ancient Greek choruses danced and sang their dramas in a semi-circular area in front of the stage. The area was known as the orkhéstra (from orkheisthai or “to dance”). The same area in opera, known as the pit, was where the musicians sat and so they became known as the orchestra.
Because the area is depressed so as not the block the audience’s view of the stage, this area became known as the pit or the orchestra pit.
Opera really reached prominence as an art form with Claudio Monteverdi’s
La favola d’Orfeo in 1607. There is no surviving full score so any version you see today is only an approximation. However, we do know the instruments to use because Monteverdi specified them:
Monteverdi - Orfeo - Rosa del ciel - YouTube
Since Monteverdi was patronized by the Duke of Mantua who spared no expense, the large orchestra was assembled and the opera’s phenomenal success ensured that future operas would have large orchestras which was essential to the evolution of the symphony orchestra.