drawing of a chest organ

  • A bit off-topic in a house organ forum, but the five buttons are the register pulls. The instrument has a register in the lower half that can be played with more wind or (quieter) with less wind. Hence two pulls. In the treble it has two stops tuned to beat and the right pull opens only the main stop, the left both at the same time. In the middle there is a tremulant, but in the French harmoniums working with pressure wind it is always very violent and causes rather fast periodic interruptions of the tone. I don't know what this was used for in the past, but I think it sounds awful. Maybe it can be adjusted to make it sound smoother, but I've heard it on many such instruments, and it was never pleasant.

    The organ builders in the early 19th century were fascinated by the possibility of using free-swinging reeds to make volume changes without deviations in pitch! Therefore several (even Cavaillé-Coll) constructed Harmoniums before the professions of organ- and harmonium-builder split up. And Harmonium stops were sometimes even built into large romantic organs as swell! If you look at it this way, the harmonium was the dominant form of the house organ between about 1850 and 1950, and is therefore not off-topic here.

  • Dear friends of organ builders,

    I have a question is how to prepare the L shaped closed pipe, where to make the cut? Is there any certain rules?

    The physics of the closed pipe resembles to one closed end pipe, as shown in the gragh below. So, Do I need to cut at the place of a 'node' of a harmonics, in such case to let the 'turning' of the wave not to be disturbed much?

    I think for closed pipe, the strongest sound is the fundamental tune and the 3rd harmonics, so to make the cut, do I need to just avoid the anti-node of the 3rd harmonics?

    Best regards,



  • Hi Xiaohu, the position where you place the miter isn't critical. Some builders make a two-times-45-degree miter to improve sound, but I think it's only worth it for open pipes. I had some problems with an open pipe that had two miters (the principale c pipe in my organ), but it's rather the narrow scale that caused that trouble. As long as the air can oscillate at the miter, it will work. In case of doubt, just glue in a block of wood at the miter to have a "45 degree wall" for the air to bump against. I will have a look if I have some pictures of that. Regards, Jens

  • Hello Xiaohu, your keyboard is ending on note E. That's a bit strange because the "usual" compass is rather up to a2 (renaissance), c3 or d3 (baroque) or f3/g3 (later). If you prefer to play music after the baroque era, I would suggest to go up to at least f3 which is one note more as far as I can tell. Regards, Jens

    Hi Jens, I finally understood why Mr. Theo Koele's design of the keyboard is ended on the note E3. The span of the pipes actually ended in d3, a total of 51 pipes, thus the keyboard can transpose two semitones lower (440-415-392). I think that is the reason. And also thank you for answering the L shape pipe design. Best, Xiaohu

  • Dear fellow organ friends,

    It is been a bit busy recently, but some updates on the drawings of the chest organ, the placement of the organ pipes have been finished, but 8 pipes have been cut into L shape and the C#pipe is made into U shape. Next I will continue to draw the below and the blower. Looking forward to your valueable advices.