An Orthodox choir's duty is primarily to give glory to God, and secondarily to lead and inspire the congregation in prayerful and attentive worship.
At All Saints, we are blessed with vibrant congregational singing. Because of this, the choir's role is less proactive than in many churches. Since the congregation knows and sings most of the hymns, the choir can be content with simply setting the pitch and the tempo. Rather than lead the congregation by pushing them into more complex and difficult (even if also more beautiful) arrangements, the choir's real struggle should be to lead by setting an example of how one should worship (including singing) in an Orthodox church: prayerfully, thoughtfully, and attentively.
Since the choir is such a prominent and visible participant in the Liturgy, involvement should be treated with a level of sobriety and seriousness comparable to that of serving on the altar. Thus, though exceptions are sometimes made, catechumens and inquirers are discouraged from joining; only baptized and chrismated Orthodox Christians should assume such a prominent position in the church. In addition to the liturgical importance of singing sacred music in the Orthodox Liturgy, commitments such as choir can unnecessarily complicate the process of really learning how to pray and worship in the Church.
If you would like to sing in the choir, it would be ideal to talk to the director beforehand. Though choir is to be taken very seriously, the time commitment at All Saints is minimal; practices are usually only held in preparation for major feast days or seasons with large amounts of unique material.