Imagine how difficult it must be to hold a position as an official church composer when your country changes religions. Now imagine that there were three such changes in your lifetime, and you will have some idea of the trials and tribulations of Thomas Tallis, whose 500th birthday was celebrated Saturday evening at the Church of St. Paul the Apostle. For Tallis to have kept his head – both literally and figuratively – is a testimony to his subtle compositional skills and his natural penchant for humble quietude.

Don’t feel guilty if you didn’t get anything for Tallis on this momentous occasion: No one actually knows when he was born, 1505 being but an agreedupon year. What is undeniable is that Tallis was the teacher of William Byrd, whose music was also on the program; that he composed the theme that inspired the famous fantasia of Ralph Vaughn Williams; and that he wrote his most enduring work, “Spem in alium,” in order to challenge the Italians, particularly the family at San Marco in Venice.

The music of the 16th century in England has experienced a renaissance in the past 30 years because of a cappella groups like the Tallis Scholars, who put on Saturday’s concert. The group did not perform “Spem in alium,” since it consists of 40 polyphonic parts and the scholars number only 10 – five men and five women, including the unusual pairing of a female and a male alto. Instead, they opened the Tallis portion of the evening with his “Missa Puer natus est nobis.”

The “Gloria” section is amazingly impressive, with no less than eight parts at any one time swirling and combining to produce towers of sound quite dissonant to the modern ear. The acoustics at St. Paul’s require some adaptation by the listener. The marvelous echo effects of a cathedral are there, to be sure, but there is also a somewhat skewed parabolic phenomenon that makes it seem like individual whispered words are coming from behind. More than once, I was tempted to turn around and ask my neighbors to be quiet, only to realize that the voices were coming from the singers.

The scholars intoned with absolute perfection of pitch and expert blending, melding anonymous voices into a glorious whole. It was fascinating to follow the phrase “Sancto Spiritu” through the melange of voices, and the “Agnus Dei” was sublime. It was disconcerting to have people applaud between sections of a Mass in a Catholic church, but it was also heartening to know that members of the heathen population also attend these events. St. Paul’s has a rather large footprint, and every seat was full this night.

Tallis was born a Catholic and never converted, but he kept his protestations about Protestantism under wraps, instead embedding them into his music. When the scholars performed “Lamentations I,” for example, the line “Jerusalem, return to the Lord your God” was spine-chillingly powerful. The entire Tallis set was splendid and, in this spiritual setting, a charism.

Two short works by John Taverner, who was born in 1490 (well, around then), served as curtain raisers. The evening ended with two longer efforts of Byrd: “Ave verum corpus” and “Tribue, Domine.” This music is much brighter than that of the mentor – had it been written 200 years later, we might describe it as major key to the master’s minor – but less emotionally affecting.All was conducted masterfully by the founder of the group, Peter Phillips, himself a bit of a Renaissance man. Back home in England, he may be as well known for his columns about cricket in the Spectator as he is for his musicianship.

It should also be mentioned that in a solid hour and a half of music, the choir stood throughout. This may seem superfluous now, but keep reading.

***

Christmas really began for me on Thursday afternoon, when the conductorless ensemble Orpheus offered two celebratory works at Trinity Church. Arcangelo Corelli’s “Christmas” Concerto and J.S. Bach’s “Magnificat” have in common not just their obvious seasonality, but also their unusual modular nature.

The Corelli appears to be just another widget on the assembly line of his many concerti grossi (it has an identifying catalog number of Op. 6, No. 8). But someone – either the composer himself or the arranger John Pepush of “Beggar’s Opera” fame – adapted the piece as a choral work, most likely to make it more appealing to the English churchgoing public.The vocal parts were recently recovered after having been lost for centuries, but Orpheus chose to present only the instrumental version.

I was instantly put in a mood of comfort and joy by the sweet sound of this headless band. The excellent acoustics in this Lower Manhattan venue spun the strings of the lyre of Orpheus into golden voices, which were particularly effective in the slower sections. In the more propulsive passages, the goal seemed to be not so much excitement as the suggestion of movement – a pleasant phenomenon in a concerto most gentle.

Once the Bach began, however, there were problems. “Magnificat” is modular in the sense that Bach composed it for everyday usage at St. Thomas, but added various parts to be utilized only at Christmas. “Magnificat” is a canticle – that is, a song – of the Blessed Virgin Mary (Luke I: 46-53), and as such should flow as one continuous work. There are no recitative sections in canticles, no artificial intervals of time, no unnecessary pauses.

Trinity Church may be superb acoustically, but the performance space is quite limited. In order for the choir to sit while not singing, the singers had to walk to seats away from their posts; they joined this parade about a dozen times, making a shambles of the melodic flow.This is not the “St. Matthew Passion” – “Magnificat” is only about 30 minutes. Couldn’t they have stood quietly when necessary?

In any case, the instrumental playing was noble and stately, although I can’t help but note that a conductor might have ratcheted up the tension level just a tad. The oboe d’amore soloist in the “Quia respexit humilitatem” intoned poignantly, and the trumpets controlled their notoriously difficult parts (originally written for little instruments tuned in E flat) with iron discipline.The reprise of the powerful opening music on the line “As it was in the beginning” was extremely moving.

The New York Bach Choir has apparently made the decision to forge ahead without a conductor, a la Orpheus. The singers are in dire need of an experienced leader: The tutti passages were woefully out of tune, their diction was fuzzy in many spots, and their soloists were a motley crew, some far from ready for prime time. But hey, it’s Christmas!