Charles H. Spurgeon on Psalms 144:9

Psaltery —an instrument of ten strings. Nebelazor. We are led to the conclusion that the nebel was the veritable harp of the Hebrews. It could not have been large, because it is so frequently mentioned in the Bible as being carried in processions ...The English translators render nebel (apparently without any special reason) by no less than four words; (1) psaltery, (2) psalm, (3) lute, (4) viol. The first of these is by far the most common in the Authorized Version, and is no doubt the most correct translation if the word be understood in its true sense as a portable harp. Nebels were made of fir wood, and afterwards of almug, or algum, which was, perhaps, the red sandalwood of India...With nebel is often associated the word azor, which is traced to a root signifying ten, and which has therefore been rendered in the Septuagint by by en dekacordw or as qalthrion dekacordon, (psalterium decem chordarum) or in dechachordo psalterio in the Vulgate. In the Chaldee, Syriac, and Arabic versions also are found words implying the existence of ten strings in the nebelazor. The word azor may therefore be considered as qualifying or describing the special kind of nebel to be used, much in the same way as we now speak of a trichord pianoforte. It is in our English version always rendered by the words "ten stringed." —John Stainer, in "The Music of the Bible," 1882.