When François Couperin was officially appointed to Saint Gervais in 1685, the parish was one of the most important in Paris: more than fifty priests, as many clerks, and about fifty other clergymen living on the parish area; they were all placed under the authority of the parish priest, a very important person at that time, and of the vicar.
There were also laymen, choristers, bell-ringer, organ bowers, verger, gravedigger, etc.
The parish were managed by a board of four churchwardens, being eminent officials of the State or rich traders.

The organist had a lot to do : he had to play about four hundred services a year, and also funeral services of personalities, weddings, brotherhoods holidays. So he was accommodated near the church (today rue François Miron).

The solemnity of the ceremonies looks really incredible today; in January, 1686, a while after being appointed, François Couperin had to play for funeral service of the chancellor of France, Michel Le Tellier.

The Mercure galant, a famous newspaper, describes the ceremony:

« The whole church was draped with black from panes to ground, and on the fabric were two velvet strips, with the Chancellor's armorial bearings interlaced with two maces crossed in long necklace, and tied up with the Orders of the King's collar, whose the Minister was a commander... Above the first strip were a silvered cornice of half a foot width, on which were obelisks which supported two silver lizards having in the middle a bat, and two maces put in long necklace from behind. Between these obelisks, silver candelsticks, topped by a large golden star carrying a big wax candle, had been arranged to surround the church and the two crossings, each four separated by vases on pedestals carrying big torches. There were more than eight hundred candlesticks around the church, which made an effect all the more beautiful as symmetry was regularly kept and as the hangings were filling all the choir's windows... A canopy of embroidery was above the altar...
A high stage with five degrees filled with more than hundred fifty candlesticks with candles decorated with the Chancellor's arms was at the bottom of the nef. At the four corners were four alabaster statues which could easily been recognized as the Justice, Prudence, Temperance and Faith. A canopy of black velvet with the same arms was suspended over this scene. The body of this great Minister, who since his death had been lying in his chapel, had been brought on the stage previous evening.
At ten o'clock, the Bishop of Troyes, dressed with pontifical clothes, began Mass and after the Offering, which was presented by three gentlemen, the Bishop of Meaux (i.e. Bossuet) pronounced funeral oration in the presence of the Papal Nuncio, many archbishops, bishops, dukes, marshals of France, members of the Council of State, and councillors of the Court... »

At that time, the organ's part during services was very strictly settled; in 1685 was effective the Ceremonial of Paris churches, edicted in 1662 by the archbishop. The Ceremonial prescribed not only the time when the organ had to play, but also the musical style, the music being always based upon plainsong.
It's the reason why during this period all the organ Masses or Magnificat are set on the same templates.

In 1690, being twenty one years old, François Couperin published his two organ Masses; then he won't publish any more for the organ.
In December, 1693, he was also appointed organist at the Chapelle Royale in Versailles, where four organists shared "quartiers" (quarters). He should henceforth be divided between St Gervais and Versailles.

Not much is known about Couperin's activities in Saint Gervais. He used to play on a regular basis until 1723; in 1714, he ordered a restoration of the organ by François Thierry. From 1723, he would often be replaced for the common services by his cousin Nicolas who will succeed him in 1733.