[3] From 1991, Reulein was the church musician at the Heilig Geist in Frankfurt-Riederwald, from 2000 he has held the position at Liebfrauen in the centre of Frankfurt.

[4] Reulein is known for composing new songs for church services (Neues Geistliches Lied), many of them on texts by Eugen Eckert.

[2] Reulein was from 2000[5] until 2005 the head of the Arbeitskreis Kirchenmusik und Jugendseelsorge im Bistum Limburg, caring about more appropriate church music for young people.

Reulein has been an instructor of liturgical organ playing and improvisation at the Frankfurt Hochschule für Musik und Darstellende Kunst from 2002.

[2][6] In 2014, Reulein recorded at Liebfrauen a CD of Französische Orgelsymphonik (French symphonic organ music) with works by Léon Boëllmann, Camille Saint-Saëns, Alexandre Guilmant and Charles-Marie Widor.