The instrument's exact lineage is still a matter of some debate, with scholars divided on whether the string bass is derived from the Viol (Viola da Gamba, or informally Gamba) a musical instrument of the Renaissance and baroque periods, distinguished from members of the violin family especially in having a deep body, a flat back, sloping shoulders, usually six strings; or the the now superceeding violin family.
The double bass is the largest stringed instrument, the lowest in pitch, and it is used in most every musical style, including classical, jazz, folk, rock, country and others. It has acquired many names over the years, "String bass" and "upright bass" are common alternative monikers, as are contrabass, stand-up bass, acoustic bass and bass violin. In certain types of folk, country and bluegrass music, slang terms for the double bass include; doghouse bass; bull fiddle; and bunkhouse bass. But, there is no difference in the instrument regardless of name.
The term "string bass" was coined to differentiate it from other bass instruments--such as the tuba and bass drum--in orchestral use. The names "upright," "stand-up" and "acoustic" bass are fairly new terms, first used in the mid-20th century to distinguish the bass from the electric bass guitar.
The modern double bass has four strings and is tuned in "fourths". From low to high, the strings are tuned to the notes E, A, D and G, which is also standard tuning for bass guitars (electric and acoustic).
Acoustic bass guitars now exist, but are much less common than acoustic guitars. The first modern 4-string acoustic bass guitar was developed in the mid-1950s by Kay of Chicago. Prior to that the closest thing to an acoustic bass guitar was the Mexican Guitarrón used in mariachi bands. The Guitarrón has a very large, deep-body with 6-strings (rather than 4), and a fretless fingerboard. The 6 strings and deep body might be thought of as more like a Gamba.(2)
Most double bass players use steel-core wound strings, but the use of old-fashioned "gut" or synthetic nylon equivalents strings are popular with purists.
The string bass is a standard member of the orchestra's string section, as well as the concert band, and is featured in concertos, solo, and chamber music in Western classical music. The bass is used in a range of other genres, such as jazz, 1950s-style blues and rock and roll, rockabilly, psychobilly, traditional country music, bluegrass, tango and many types of folk music.
The double bass is played:
It is not uncommon for players to use both the bow and finger-plucking methods to achieve certain sounds and playing effects. In orchestral repertoire and tango music, both arco and pizzicato are employed. In jazz, blues, and rockabilly, pizzicato is the norm.
Classical music uses the natural sound produced acoustically by the instrument, as does traditional bluegrass. In jazz, blues, reggaes, and related genres, the bass is frequently amplified.
Both arco and pizzicato playing methods were used on the song Welcome Home, and it is not amplified.
1 OUR PASTIMES, https://ourpastimes.com/difference-between-a-string-bass-a-double-bass-12305586.html
2 Guitarrón, https://en.wikipedia.org/wiki/Guitarr%C3%B3n_mexicano
3 Double String Bass, https://en.wikipedia.org/wiki/Double_bass