Michael Eimann has been a passionate singer since early childhood. He works as a freelance musician and as a singer and pianist in various music projects of different styles (including Slixs, Java Five).
As a composer and arranger he works for orchestras, theaters, films, bands and choirs.  In 2013/14, the musical director of SLIXS was commissioned to set up and direct a choir for Bobby McFerrin, as well as to write some arrangements for his European tour. In the process, he also went deeper into the magical world of Circlesongs as a singer.
For many years he has also been producer of the SLIXS albums. These have been awarded several times with the CARA (A Cappella Recording Award).

Originally from Canada, Kevin Fox is an internationally recognised singer, choral director, arranger and workshop leader. He performed with the Grammy-winning vocal group The Swingles for 12 years and has recorded with London Voices for a range of film soundtracks. Kevin has served as Artistic Director of SING! Toronto and Musical Director of the television series “Sing: Ultimate a cappella“ on Sky One. He has taught at institutions and festivals including the Guildhall in London, Europa Cantat in Estonia and Vocal Asia in Japan. He also serves as an adjudicator for Interkultur. Kevin currently directs three London-based community choirs, leads workshops in improvisation and rhythm, and occasionally writes original choral music. He encourages singers to trust their creativity, take musical risks and express themselves with confidence. His approach combines practical musicianship with an encouraging, open-minded spirit.

Oliver Gies is a composer, arranger, singer and one of the leading creative voices in Germany’s a cappella scene. After studying school music in Hanover, he went on to study jazz, rock and pop, specialising in composition and arranging, in Essen. He has worked as a freelance musician since 1998, writing and arranging music for a wide range of ensembles and leading workshops on arranging, songwriting, choral conducting and singing. As a founding member of MAYBEBOP, he plays a central role in shaping the group’s repertoire, composing, writing lyrics and arranging many of its songs. In 2020, the Recorded a cappella Review Board named MAYBEBOP its “Group of the Decade.” Oliver spent five years teaching jazz and pop choir conducting at the Federal Academy for Cultural Education in Wolfenbüttel and conducted the Lower Saxony State Youth Choir in 2012. Many of his choral arrangements have become favourites throughout the German choral community.

Katarina Henryson was a founding member of the Stockholm-based a cappella group The Real Group in 1984, helping shape its sound with her flexible alto voice and distinctive stage presence. Since leaving the ensemble in 2016, she has continued to work as a singer, artist and educator, exploring new forms of expression between music and performance. She tours regularly in Sweden and across Europe with cellist Svante Henryson, in projects that connect chamber music with other genres. Katarina is Artistic Director of the Eric Ericson International Choral Centre and leads the 360° concert series at Stockholm’s Eric Ericson Hall. She gives workshops for choirs and vocal groups and directs two choirs on Gotland. In 2026, she took part in "Keep Wonder Still Wander“, a project bringing together dancers and choral musicians for which she also wrote choral music; the project continues in 2027. She is also involved in an art project in Basel with the Fondation Beyeler.

Merel Martens is a choir director, arranger, teacher and vocal coach. In 2015, she graduated with the highest honours from the Vocal Leadership master’s programme at the Royal Academy of Music in Denmark. Her work has been shaped by Jim Daus Hjernøe, Peder Karlsson and Roger Treece. In the Netherlands, she is known for her work with award-winning vocal groups such as Pitch Control, MAZE and VOÏSZ Vocal Projects. She also coaches professional ensembles across several countries, including The Junction, Perpetuum Jazzile, Vocalocity and The Keystones. In 2014, she founded the Dutch Organic Choir, a group built around rotating leadership and partly improvised original vocal music. Merel leads workshops for choir directors and vocal groups, with a particular interest in circlesongs, pop repertoire, vocal games and Vocal Painting. She aims to create a positive rehearsal space where everyone feels safe and free to contribute.

Kim Nazarian (USA) is a world-renowned, Grammy-nominated jazz vocalist, recording artist, educator and lecturer. A sought-after soloist, she has performed around the globe and helped shape the sound of the acclaimed vocal group New York Voices for more than 36 years. She brings her extensive experience as a performer to her work as an educator: at Ithaca College, she teaches jazz singing to students specialising in vocal jazz. She also shares her perspective on music and life as a working musician through private lessons in her own studio, as well as workshops and masterclasses internationally. Her work further includes serving on festival juries and guest-conducting singers at a wide range of experience levels. Across these settings, Kim combines deep musical knowledge with a generous, practical approach to singing, ensemble collaboration and artistic expression, encouraging singers to develop their skills and confidence while finding their own musical voice.

Essi Wuorela has been an original member of Rajaton since 1997. The internationally acclaimed six-part Finnish a cappella group has toured around the world, released numerous celebrated albums and created programmes featuring songs by ABBA, Queen, the Beatles and the Bee Gees. Alongside her work with Rajaton, Essi has pursued a varied solo career. Her first solo album appeared in 1994 and achieved gold status in Finland. As a freelance singer, she has contributed to recording projects and performed with ensembles, pop and rock bands, and orchestras, including the Tapiola Chamber Orchestra and the Oulu and Lahti Symphony Orchestras. She is also a member of EVA Trio, whose distinctive sound combines voice, cello and kantele in a meeting of Finnish folk traditions and contemporary influences. One of the trio’s recent projects is a musical programme for children, reflecting her curiosity and interest in new ways of reaching audiences.