There’s this one:
http://www.ccwatershed.org/media/pdfs/13/10/10/22-18-18_0.pdf

My personal go-to is “O God come to my assistance. O Lord make haste to help me”

We chant the Pater Noster, Ave Maria, and the Gloria Patri at the end of our vocal and physical warm-ups. Cantors chosen at random, to demonstrate that we are all called to the apostolate of prayer, and that we need to support one another in this vocation - no matter the time, place, or pitch chosen!

Oh Lord, what have I done or what sins did my parents commit that brought me to this place...?

Actually, it isn't that bad. I like the St. Michael prayer, Our Father and a prayer to the Holy Spirit. I also ask for patience with my singers who seem incapable of getting anywhere on time.

Many years ago (in Walsingham's early days) I composed brief 'offices' for my choirs to be said before mass (A below) and before a rehearsal (B below), and after a rehearsal. My choirs in those years valued these offices, which served to 'consecrate' their sacred endeavours. These 'collects' may be somewhat prolix, but they may provide any interested parties with ideas for their own prayers - as if the excellent ones recommended in the above comments are not enough!

A: The Collect from a Choir Office before mass -
Choirmaster - O Most Holy and Immortal God, before whose throne thine Angels ever sing, and whose face the Blessed Ones see: send, we pray thee, thy Holy Spirit into our midst, and, of thy goodness, create in us pure hearts and cleanliness of mind, body, and soul; to the end that with some semblance of that heavenly song and blessedness, we, who are about to acclaim thee in thy Holy Mysteries and offer unto thee the sacrifice of praise, may, together with our brethren whose praises we lead, come to know thee more truly, love thee more dearly, serve thee more fully, and praise thee more meetly. Through Jesus Christ our Lord, who livest and reignest with thee and the Holy Ghost, ever one God, world without end. R. Amen.

B. The Collect from a Choir Office before a rehearsal -
Choirmaster - O God, who didst inspire thy servant David to write songs and to appoint singers for thy worship: send thy Holy Spirit our souls to inspire, that, with true joy and diligence, we may accomplish those things which thou hast set before us for the praise and glory of thy Name, and for the aedification of ourselves and our brethren; let us ever be mindful that thou hast called us to service and fulfillment through the perfection of those gifts which thou hast bestowed so graciously upon us. Through Jesus Christ our Lord, who livest and reignest with thee and the Holy Ghost ever one God, world without end. R. Amen.

As I look back, these 'collects' are prolix indeed. Perhaps they will provide some ideas. The astute reader will detect that I 'borrowed' a few ideas from elsewhere.

The offices themselves (which were sung in toto) took less than five minutes and consisted of the Trinitarian invocation, brief preces and responses, a short musically oriented psalm, a very brief musically oriented 'chapter', Our Father, Hail Mary, Collect, and 'Let us go forth in peace' & 'Thanks be to God'.
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I especially like what Sponsa Christi linked above.

Do you plan...

No.
They're on permanent loan.

We always have a prayer before beginning our choir practice and before Mass. At choir practice the music director reads a small prayer from a small prayer book, we then pray for each others intentions. We also have a closing prayer at choir practice which consist of chanting the Divine Praises by Jacob Schloeder. Before Mass we thank God for all the members who came and generally pray the Our Father.