Music nibs were developed in the 1930s. Characteristic is a broad but flatly ground nib with which thin and broad lines, and thus calligraphic effects, can be achieved. The most conspicuous feature is the doubly slitted nib with two breather holes, or heart holes; the double slitting carries approximately twice the quantity of ink forward to the tip of the nib.
These nibs are designed for writing with very light pressure or none at all, which is why skipping scarcely occurs. If greater pressure is applied, the ink flow rises noticeably and the written image appears considerably livelier than with normal nibs. Too much pressure should nevertheless be avoided: the double slit does make the nib more flexible, but it also bends out of shape more quickly. Because of the sharp grind it also tilts easily, so that such pens are not suitable for writers who already have difficulty with OM nibs. Music nibs were only rarely fitted in Montblanc fountain pens; a Montblanc 344 N from about 1957 to 1960 is among the documented examples.