Bass violin is the modern term for various 16th and 17th-century bass instruments of the violin (i.e. "viola da braccio") family. They were the direct ancestor of the modern cello. Bass violins were usually somewhat larger than the modern cello, but tuned the same or sometimes just one step lower than it. Contemporary names for these instruments include "basso de viola da braccio," "basso da braccio," or the generic term "violone," which simply meant "large fiddle." The instrument differed from the violone of the viol, or "viola da gamba" family in that like the other violins it had at first three, and later usually four strings, as opposed to five, six, or seven strings, it was tuned in fifths, and it had no frets. With its F-holes and stylized C-bouts it also more closely resembled the viola da braccio.
The name "bass violin" is also sometimes used for the double bass.
Occasionally historians have used the term "bass violin" to refer other various instruments of the violin family which were larger than the alto violin or viola, such as the tenor violin. This use can be synonymous with "harmony violin."
After the 1950s, the term "bass violin" may refer to a bass instrument of the violin octet.
The bass violin was developed in Italy in the first half of the sixteenth century, to be in consort with the violin and viola. The first builder was possibly Andrea Amati, as early as 1538. The first specific reference to the instrument was probably made by Jambe de Fer in his treatise Epitome Musical (1556). One of the first known instances of a composer explicitly calling for the bass violin ("basso da brazzo") was Monteverdi in Orfeo (1607) (the first was possibly Giovanni Gabrieli in Sacrae symphoniae, 1597).
The viol, or viola da gamba, was introduced to Italy from Spain around 1490. Before the introduction of the viol, no bowed instrument existed in the region which was played in the a gamba position (i.e., between the legs, the way the cello is played today, as opposed to the violin, which is held under the chin). The viola da gamba was also much larger, and therefore could play much lower notes than the other fiddles that existed in Italy at that time. The first Italian viols (or "violoni" as they were often called) soon began to take on many characteristics of the precursors to the violin, such as separate tail pieces, and arched bridges that allowed to player to sound only one string at a time. (Though paintings like Jan Brueghel the Elder's "The Rustic Wedding" and Jambe de Fer in Epitome Musical suggest that the bass violin had alternate playing positions, these were short-lived and the more practical and ergonomic a gamba position eventually replaced them entirely.) One of the qualities that was almost certainly adopted by the Italian violin makers from the early Spanish viols was the C-bout, which they soon stylized. At some point in the early to mid-sixteenth century, an Italian maker (possibly Amati) set out to create a violone that was more closely matched, in appearance, tuning, and number of strings, to the new violin. Judging by artistic representations of the period, this may have been a somewhat gradual development. For example, there are depictions of instruments that appear to be bass violins (such as the one in Gaudenzio Ferrari's Glory of Angels, c. 1535), but that clearly show the presence of frets. Once the distinction became clear, and the form of the bass violin had crystallized, theorists and composers began to refer to the new instrument as the "basso da viola da braccio," or the first true bass violin.