Music in the worship of reformed Lutheran and Calvinist churches has a form of music that has been adapted to the ideological basis of the church. The form of hymn song is one of the church doctrines that must be carried out by church members. However, in its development, the reformed churches began to transform with the transform of hymns music arrangements into popular music compositions. So that the hymn song no longer matches the characteristics that are based on the rules of hymnology. Therefore, this research intends to analyze the transformation process of hymns arrangement which is usually sung in the worship of the reformed church, especially the local church, the Evangelical Christian Church in Minahasa (GMIM) located in GMIM KristusManado. This research was conducted based ona qualitative research method with descriptive analysis. In collecting data, researchers conducted a literature review and collect relevant information through online media, field observations by visiting churches that had composed hymns, and conducted in-depth interviews. The results of this study found the process of transformation of hymns song in varied Beat ostinato Element. There are elements of composition that changedthe form of melodic accompaniment, the develop popular rhythms, minimizing the progression of harmony, and have implications for changes in the structure of song form. The tendency of music in the church also prioritizes popular music aesthetics, at the same time considering the essence of thesong hymns. On the other hand, the arrangement of components in the hymn song to trigger the attraction and motivate the congregation in creative worship. Especially for young people in unstable and frequently move in varying churches. So that, hymn song, transforming to reach them and stimulate their enthusiasm in worship. This research is expected to be useful in the field of church music, especially music analysis studies, and rely on a social-cultural perspective to learn the current disruptive era.