The Latvian Radio Choir. (Claudia Hoehne)

Latvia basked in the spotlight Friday evening with a concert by one of its leading musical groups at the Library of Congress. The Latvian Radio Choir marked the centenary of Latvia’s independence with a powerful program of unaccompanied gems. Andris Teikmanis, the Latvian ambassador to the United States, spoke proudly of his country, small in size but “a great musical power in the world” nevertheless.

The choir of 24 singers is renowned, particularly for its interpretations of music from the past hundred years. Conductor Sigvards Klava deftly led them through their signature repertory, as well as recent pieces by Latvian composers Peteris Vasks and Eriks Esenvalds.

“Our Mother’s Names,” by Vasks, brimmed with yearning glissando chords, straining upward and downward until the piece dissolved in a fervor of avian whirs and whistles — and not a musical instrument in sight.

Surprise came in some odd but effective arrangements of Gustav Mahler. Clytus Gottwald’s choral transcription captured the transcendent isolation of Mahler’s song “Ich bin der Welt abhanden gekommen,” with some voices approximating the accompaniment and others handing the melody from one section to another.

Gott­wald’s version of “Die zwei blauen Augen” ranged from bleakly quiet to towering forte sonorities.

Not all of these arrangements worked: Gérard Pesson’s transcription of the “Adagietto” from Mahler’s Symphony No. 5 could not achieve the same effect as the original strings. However, Gott­wald may have surpassed his model with his arrangement of the “Louange à l’Éternité de Jésus” movement from Olivier Messiaen’s “Quatuor pour la Fin du Temps.” Expanding the piano part in broad, luscious chords for amassed voices added to the timeless scope of this piece, as mysterious, glistening harmonies undulated under the arching melody.

The choir produced similar slow-moving textures in Arvo Pärt’s “Nunc dimittis,” with the melody morphing imperceptibly from section to section over a full dynamic range. The only shortcoming of this performance was in older music, with selections by Giovanni Gabrieli sounding plain and tame by comparison. The ensemble responded more vibrantly when older music was tricked out with modern trimmings, like Sven-David Sandström’s updated version of Henry Purcell’s “Hear my prayer, O Lord” and Igor Stravinsky’s arrangement of Carlo Gesualdo’s three motets.