Bumbulum, Bombulum or Bunibulum, a fabulous musical instrument described in an apocryphal letter of St Jerome to Dardanus, and illustrated in a series of illuminated MSS. of the 9th to the 11th century, together with other instruments described in the same letter. These MSS. are the Psalter of Emmeran, 9th century, described by Martin Gerbert, who gives a few illustrations from it; the Cotton MS. Tiberius C. VI. in the British Museum, 11th century; the famous Boulogne Psalter, A.D. 1000; and the Psalter of Angers, 9th century. In the Cotton MS. the instrument consists of an angular frame, from which depends by a chain a rectangular metal plate having twelve bent arms attached in two rows of three on each side, one above the other. The arms appear to terminate in small rectangular bells or plates, and it is supposed that the standard frame was intended to be shaken like a sistrum in order to set the bells jangling. Sebastian Virdung gives illustrations of these instruments of Jerome, and among them of the one called bumbulum in the Cotton MS., which Virdung calls Fistula Hieronimi. The general outline is the same, but instead of metal arms there is the same number of bent pipes with conical bore.
Virdung explains, following the apocryphal letter, that the stand resembling the draughtsman's square represents the Holy Cross, the rectangular object dangling therefrom signifies Christ on the Cross, and the twelve pipes are the twelve apostles. Virdung's illustration, probably copied from an older work in manuscript, conforms more closely to the text of the letter than does the instrument in the Cotton MS. There is no evidence whatever of the actual existence of such an instrument during the middle ages, with the exception of this series of fanciful pictures drawn to illustrate an instrument known from description only. The word bombulum was probably derived from the same root as the βομβαύλιος of Aristophanes (Acharnians, 866) (βόμβος and αὐλός), a comic compound for a bag-pipe with a play on βομβυλιός, an insect that hums or buzzes (see Bag-Pipe). The original described in the letter, also from hearsay, was probably an early type of organ.
 Ad Dardanum, de diversis generibus musicorum instrumentorum.
 De Cantu et Musica Sacra (1774).
 For illustrations see Annales archéologiques, iii. p. 82 et seq.
 Musica getutscht und aussgezogen (Basle, 1511).