Billy Kristanto graduated from Hochschule der Künste in Berlin, Germany, where he majored in harpsichord under Mitzi Meyerson. He furthered his studies in harpsichord and fortepiano under Ton Koopman and Stanley Hoogland, and received his postgraduate certificate from The Royal Conservatory in The Hague, Netherlands. In 2009, he successfully defended his doctoral thesis titled “Musical Settings of Psalm 51 in Germany ca. 1600-1750 in the Perspective of Reformational Music Aesthetics” under the guidance of early music specialist Prof. Dr. Silke Leopold at the University of Heidelberg, Germany. His second doctoral degree in systematic theology was conferred in 2011 following the completion of his dissertation on "The Glory of God in the Thought of John Calvin".

Particularly interested in historically-informed practice, Billy has given musical direction to several oratorio societies and performances in major cities in Indonesia, Singapore, Hamburg, and Berlin. He also lectures at The International Reformed Evangelical Seminary.

Billy also writes articles on music for international journal, presents papers on music at international conferences. Among his writings are “Reformation and Music” (Unio cum Christo 3 [2017]), “Pop Music, Pragmatism, and Christianity” (Ethos Institute, 2017), The Place of Music in the Church and in Society (Singapore: Sower Publishers, 2018), “Calvin dan Potensi Pemikirannya bagi Ibadah Kristen” (Veritas 19/2 [2020]), “Exil und religiose Identität in einigen Kantaten von Johann Sebastian Bach” (European Journal of Theology 29/2 [2020)”, “The Beauty of Music” (Ethos Institute, 2022), “Ars Moriendi, The Art of Dying” (Ethos Institute, 2022), “J. S. Bachs Sterbekantaten im Lichte der lutherisch-orthodoxen und spätmittelalterlichen ars moriendi” (Evangelische Theologie 83/6 [2023]), and “Mirror, mirror on the wall, who’s the most beautiful of them all?” (Ethos Institute, 2024).

As an ordained pastor at Gereja Reformed Injili Indonesia, Billy currently serves the International Reformed Evangelical Church in Berlin, Hamburg, Munich, Switzerland, and Stockholm (irec-europe.org).

Calvin Abdiel, an Indonesian-Australian pianist, was born in Indonesia in 2001 and showed an early passion for classical music. After moving to Australia in 2011, he continued his musical education at the Sydney Conservatorium, where he completed his Bachelor of Music (Performance) with First Class Honours under the guidance of Natalia Ricci.

After obtaining a Master of Arts degree under Prof. Eldar Nebolsin at the HfM Hanns Eisler Berlin, supported by the DAAD Postgraduate Scholarship and the SCM George and Margaret Henderson Overseas Postgraduate Scholarship, Calvin is currently undertaking Konzertexamen in HfMT Hamburg under Prof. Stepan Simonian.

Calvin has won numerous prizes at international competitions, including the George Frederick Boyle Third Prize and the Nancy Weir Best Australian Pianist Prize at the Sydney International Piano Competition 2021. Following the competition, he embarked on a debut recital tour across Australia. Other awards include 2nd Prize at the International Competition for Young Pianists “Steps to Mastery” in 2017 and 1st Prize at the Ananda Sukarlan Award International Piano Competition in 2020. He has performed with renowned orchestras such as the St. Petersburg State Capella Symphony Orchestra and the Queensland Symphony Orchestra, playing Prokofiev’s Piano Concerto No. 4 at the opening concert of the G20 Orchestra 2022. Calvin has given concerts in several countries, including Australia, Austria, Russia, and Germany, and has participated in major festivals.

His live performances in Australia have been recorded by ABC Classic FM and Fine Music FM. In June 2024, he released his debut CD, Themes and Variations, on Eloquence and Decca Australia.

Alongside his concert career, Calvin is actively involved in music ministry and choir training at IREC Berlin. Previously, he also served as conductor of the youth orchestra of IREC Sydney, the Cantate Deo Chamber Orchestra.

Tamariska Kristianto is an Indonesian violinist and violin teacher at the Leo Borchard Music School in Berlin. She teaches children with great passion, combining musical precision with playful creativity to inspire a love of music from an early age.

Since 2008, she has devoted herself to the violin and has gained valuable experience through masterclasses with renowned musicians such as Ulf Schneider, Cho-Liang Lin, Gia Jashvili, Francesco Parrino, Jahja Ling, and Hao Li Lin. She has received several awards, including first prize at the 2014 Violin Competition in Semarang.

As a soloist, she performed at the Simfoni Pemuda (Youth Symphony Concert) in the Aula Simfonia Jakarta in 2016 and gave solo recitals in 2015 and 2023. She also performs regularly in various chamber music formations, including quartets, trios, duos, and quintets.

After completing her studies at Hochschule für Musik, Theater und Medien Hannover, Tamariska has been actively involved at IREC Berlin, where she serves as both pianist and violinist and leads the children’s ensemble.

The IREC Europe Choir was founded alongside the church in 1999 as part of the church's ministry to praise God and share His blessings through worship. The works performed contain both textual and musical content to bring people closer to God. The choir performs a diverse range of church music; from Baroque composers such as Heinrich Schütz, J.S. Bach and G.F. Händel, to the Romantic period with Mendelssohn, and to classical modernism with Paul Hindemith.

Rev. Dr phil., Dr theol. Billy Kristanto, leads the rehearsals together with a musician trained from the choir. The choir rehearsals take place both once a week together on the Sunday before the service in the church and individually for each voice using digital media at home. Around 10 to 20 singers sing in the choir, who are both church members and active parishioners.

The choir usually sings during services, accompanied by piano or organ, at Sunday services, Christmas services and other festive services such as Good Friday, Easter and Whitsun.

In July 2010, the IREC Berlin church choir, together with the choir of the Reformed Oratorio Society Singapore, organised a "Music Evening &Angklung Ensemble in Praise of God", presenting works by J.S. Bach, Mendelssohn, J. Brahms, J.H. Schein, H. Schütz, A. Hammerschmidt and Mozart.

In 2012, the choir also sang in a revival service with "Vater unser im Himmelreich", J.S. Bach BWV 416 and "Ich bin die Auferstehung", H. Schütz SWV 324.

Over the years, the IREC Europe Choir has achieved a great deal. The choir has always actively participated in our annual church camps and has also been involved in pastoral work in prisons and retirement homes.

In 2023, the IREC Europe Choir had the privilege of performing Schubert's Psalm 23 during Stephen Tong's Gospel Rally, sharing the message of God's Word through the beauty and power of music.

Most recently, the IREC Berlin Choir performed D. Buxtehude's Membra Jesu Nostri (BuxWV 75) in two concerts—first in Berlin in the fall of 2024, and then in Hamburg in the spring of 2025.