Musicam Sacram:

VI. Sacred Instrumental Music

62. Musical instruments can be very useful in sacred celebrations, whether they accompany the singing or whether they are played as solo instruments.

"The pipe organ is to be held in high esteem in the Latin Church, since it is its traditional instrument, the sound of which can add a wonderful splendor to the Church's ceremonies and powerfully lift up men's minds to God and higher things.

"The use of other instruments may also be admitted in divine worship, given the decision and consent of the competent territorial authority, provided that the instruments are suitable for sacred use, or can be adapted to it, that they are in keeping with the dignity of the temple, and truly contribute to the edification of the faithful."43

63. In permitting and using musical instruments, the culture and traditions of individual peoples must be taken into account. However, those instruments which are, by common opinion and use, suitable for secular music only, are to be altogether prohibited from every liturgical celebration and from popular devotions.44

Any musical instrument permitted in divine worship should be used in such a way that it meets the needs of the liturgical celebration, and is in the interests both of the beauty of worship and the edification of the faithful.

64. The use of musical instruments to accompany the singing can act as a support to the voices, render participation easier, and achieve a deeper union in the assembly. However, their sound should not so overwhelm the voices that it is difficult to make out the text; and when some part is proclaimed aloud by the priest or a minister by virtue of his role, they should be silent.

65. In sung or said Masses, the organ, or other instrument legitimately admitted, can be used to accompany the singing of the choir and the people; it can also be played solo at the beginning before the priest reaches the altar, at the Offertory, at the Communion, and at the end of Mass.

The same rule, with the necessary adaptations, can be applied to other sacred celebrations.

66. The playing of these same instruments as solos is not permitted in Advent, Lent, during the Sacred Triduum and in the Offices and Masses of the Dead.

67. It is highly desirable that organists and other musicians should not only possess the skill to play properly the instrument entrusted to them: they should also enter into and be thoroughly aware of the spirit of the Liturgy, so that even when playing ex tempore, they will enrich the sacred celebration according to the true nature of each of its parts, and encourage the participation of the faithful.

To be fair, the GIRM allows use of the organ for voluntaries in the season of Advent. #313 is the "cover" for this.

That said, anything much louder or more active than the "quiet" Nun komm setting by Bach is probably too much. I would definitely not play preludes, either. Just my $0.02.

We don't have any organ during prelude, postlude, or "walking" moments in Advent. Repertoire selections are much easier that way ;-)

Rachel,

Thank you for posting.

Your job is to play music when it is normally expected to be played. It is the custom in your church to have the organ play after the service. If the pastor wants to follow the strict rules, which are almost universally ignored today, about not having the organ playing before and after Mass, then don't play. Otherwise, not playing would bring attention to the fact that you are not playing...and people would be distracted. Instead of sitting or kneeling and praying after Mass, some would be thinking, "Why isn't she playing."

IF the pastor decides to eliminate organ music during Advent, he would make an announcement or put it in the bulletin, since he is the one who makes the decisions about how closely the rubrics are followed.

You will find some chorals like the one you like to play here:

http://imslp.org/wiki/Chorale_Preludes_(Pachelbel,_Johann)

And some nice organ Music for Mass as well:

hhttp://imslp.org/wiki/Album_Grégorien_(Gigout,_Eugène)

Much of the music in these two books is written so pedals are optional!

Thank you for posting your question. We need more organists and welcome you to the fold.

Thank you very much everyone. Yeah, my pastor does not say anything about not playing prelude/postlude during advent/lent. I am quite new to organ playing. There is another organist in my church who plays before, during communion and after church all the time and I pretty much follow his tracks. Thanks for letting me know about these. I will clarify with my pastor before playing next time.
Thanks,
Rachel

No "solo" preludes in my Presbyterian work church for Advent. Instead we have the candle lighting with a piece to go along with the reading for that week and so on...last year we used Bernadette forgetherlastname's Christ Be our Light for that through Advent-stuff like that. I still do offertory music though, generally something suited to the season. So yeah, just do whatever fits your situation and applicable rules/regulations/traditions/etc. good luck!