Question: Who is the Estonian composer of classical and religious music that was featured in the recording of twenty one duets for two cellos and piano or harp ranging from the sixteenth to the twenty-first century?
Context: Eduard Oja (January 17, 1905 in Palupõhja - April 16, 1950 in Tartu) was an Estonian composer, conductor, music teacher and critic.  His father was a forest warden.  Between 1919-1925 he studied at Tartu Teacher's College at Tartu University, where he met Eduard Tubin, and he also worked for some time as a school teacher.  He was not a particularly prolific composer, composing mainly orchestral and ensemble works and choral music.  He was however much appreciated during his lifetime, and received awards and acclaim for several of his works.  He also worked as a conductor, leading the Tartu Women's Singing Society’s Women's Choir between 1930 and 1934, as well as a teacher of music theory at Tartu Higher School of Music.  In addition, he was himself a practising violinist.  A number of his works such as the opera Oath Redeemed (Estonian: "Lunastatud vanne" ) and the choral work The Return Home (Estonian: "Kojuminek" ) have been lost, although the majority of his work has survived, and is valued in museums in Estonia today.  The Eduard Tubin Museum of Alatskivi Castle contains exhibits related to him and his fellow students under Heino Eller, known as the "Tartu school", such as Eduard Tubin, Alfred Karindi, Olav Roots and Karl Leichter. Artur Lemba (24 September 1885, Tallinn – 21 November 1963, Tallinn) was an Estonian composer and piano teacher, and one of the most important figures in Estonian classical music.  Artur and his older brother Theodor (1876-1962) were the first professional pianists in Estonia to give concerts abroad.  Artur's 1905 opera "Sabina" was the first opera composed by an Estonian.  His Symphony No. 1 in 1908 was the first symphony composed by an Estonian. A Tale of Two Cellos is a recording of twenty one duets for two cellos and piano (or harp) ranging from the sixteenth century, Monteverdi, to the twenty-first century, Arvo Pärt. In classical music, a string sextet is a composition written for six string instruments, or a group of six musicians who perform such a composition.  Most string sextets have been written for an ensemble consisting of two violins, two violas, and two cellos. Allt-y-Bela, Llangwm, Monmouthshire, is a house of late medieval origin with additions from the sixteenth to the twenty-first centuries.  During the early seventeenth century, it was owned by Roger Edwards, a wealthy Midlands merchant and the founder of Usk Grammar School.  Edwards made significant alterations in the Renaissance style to the medieval cruck house.  By the twentieth century, the house was in ruins until restored by the Spitalfields Historic Buildings Trust in the early twenty-first century.  Now owned by the garden designer Arne Maynard, the house is a Grade II* listed building recognising its significance as an "exceptionally important sub-medieval house with ambitious early renaissance additions." Arvo Pärt (] ; born 11 September 1935) is an Estonian composer of classical and religious music.  Since the late 1970s, Pärt has worked in a minimalist style that employs his self-invented compositional technique, tintinnabuli.  Pärt's music is in part inspired by Gregorian chant.  His most performed works include "Fratres" (1977), "Spiegel im Spiegel" (1978), and "Für Alina" (1976).  Pärt has been the most performed living composer in the world for five consecutive years. William Paxton (1737–1781) was a cellist in England.  He composed several sets of duets and solos for the cello, including six duos for two cellos (Op. 1), eight duos for violin and cello (Op. 2), six solos for violin (Op. 3), four solos for violin and two for the cello (Op. 4), twelve easy lessons for cello (Op. 6).  and six solos for cello (Op. 8).  Paxton’s brother Stephen also composed for the cello. Pari intervallo is a composition by Estonian composer Arvo Pärt, written in 1976 in four parts without fixed instrumentation.  The composer later made versions for organ (1980), four recorders (1980), clarinet, trombone and string orchestra (1995), saxophone quartet (2002), two pianos or piano duet (2008), and eight or four cellos (2010).  "Pari intervallo" was one of seven works premiered in 1976 under the title tintinnabuli, the name of compositional style created by the composer. The Kennedy Experience is a music group and eponymous instrumental album conceived and produced in 1999 by violinist Nigel Kennedy.  The album is largely derived from the music of rock guitarist Jimi Hendrix and the title references his group The Jimi Hendrix Experience.  According to a BBC interview with Kennedy, the violinist stated that the recording is "an album of music inspired by Jimi Hendrix.  It is an extended instrumental work in six movements, each movement a classical interpretation of a Hendrix song".  On the recording, Kennedy is accompanied by seven other musicians, and the lineup includes two cellos, an oboe, two guitars, a Dobro, flute, and double bass.  With cellist Lynn Harrell, he has recorded an album of duets. Markus Robam (born February 11, 1991) is an Estonian composer and singer songwriter.  He studied audiovisual composition in the Estonian Academy of Music and Theatre and is a member of Estonian Composers' Union since 2015.  Markus Robam has released multiple studio albums including "Astir".  He has been featured on festivals "Fundamento", Tallinn Music Week, Estonian Music Days, festival Pulsar in Copenhagen , festival "Segnali" in Perugia and also performed at the “Nuova Consonanza” Festival in Rome, Italy.
Answer: Arvo Pärt