The ab Yberg Positive Organ came to the Basle Historical Museum in 1927 from the collection of Heinrich Schumacher of Lucern in whose possession it had been since early in the century. For some three hundred years it belonged to the descendents of Kaspar ab Yberg, and from 1592 it had been housed  in their family chapel. During its period of use the organ was many times repaired with patches cut from old letters, and members of the family can be identified from these fragments as late as 1692.

Judging from its compass of F to a” the organ probably dates from around 1550. Its range of 3 1/3 octaves reflects the practice current in Northern Europe from the last quarter of the 15th century until the middle of the 16th. After 1550 the most common compass was 4 octaves from C/E to c’”. Composers as late as Frescobaldi most frequently remained within F to a”.

The instrument is pitched at a444 at the museum, though our specifications call for a440. The tuning is maintained in a mean tone temperament in approximation of its original adjustment. The sound of the organ is full and rich, characterized by broader, more fundamental sounds in the lower octaves with increasing harmonic richness toward the top. The pipe scaling in comparison with modern ratios tends to larger diameters at the bottom, becoming narrower in the upper pitches. The pipe materials are lead and tin alloys; the principal is about 45% tin, while the others range from 40% down to 25%. The mouth widths are all 1/4 of the circumferences. The mouth heights are straight, and most are equal to 1/4 of the mouth width. The wind pressure is 36mm.