The organ is an instrument built into a building. Selecting a variety of sounds for an organ composition which requires more than two is a new task on each different organ, and the varieties and combinations are essentially endless. In this chorale prelude in "trio" texture, three distinct organ sounds make up the musical texture, each with a distinct job.

Bach's mastery of organ composition was demonstrated not just by long showy fugues and toccatas. The Orgelbüchlein is a collection of short chorale preludes in artful style and with the theological purpose of spanning the themes of the liturgical church year. 

"Ich ruf zu dir, Herr Jesu Christ" is unique in texture for the Orgelbüchlein and distinctly known as a passionate and desperate call in time of need. It proves that an instrument as old and architecturally fixed as the church organ has the emotional power to convey this human condition. 

Leo van Doeselaar plays: https://www.bachvereniging.nl/en/bwv/bwv-639/

Piano transcription, Tatiana Nikolayeva: https://www.youtube.com/watch?v=n0zw7CaplFY