A double bass is actually called a contrabass and is used primarily in symphony orchestras, jazz music and rockabilly music. Another name for this bass is upright bass. The contrabass has the same open strings as a bass guitar and has the same range. The strings can be steel or gut and can be either plucked or played with a bow like a violin. Its musical versatility makes the contrabass a popular instrument among bass players from all musical walks of life. Learn how you can play a double bass and take advantage of this instrument's rich diversity.
Familiarize yourself with the instrument. The open string are, from thinnest to thickets, G,D,A,E. The notes go up from there, one half step at a time., following the musical scale. This means if you start by playing the first (thinnest string) G, you will get these notes as you play each fret: G, G#, A, A#, B, C, C#, D, D#, E, F, F#, and the octave G at the twelfth fret. Do keep in mind that the double bass is fretless, meaning there are no fret markers on it like there are on an electric bass, so you will need to get used to hitting the right rights by "feel." Typically, the frets will be spaced the length of your four fingers spread.
Practice both plucking and bowing the strings. A double bass is frequently played both ways. Symphonic music will most often require the bow. Other musical forms, especially jazz and rockabilly, make use of plucking the strings. It's a good idea to become familiar with both styles of playing. Plucking is when you fret a note and pull (or pluck) the note. To achieve sound with a bow, you will fret the note you want to play and draw your bow across the note with a firm pressure. You create rhythm with the bow by moving it back and forth.
Learn to read music in the bass clef. This isn't necessary if you can play by ear, but knowing how to read music is a good skill to have for any musician. Music for the double bass is written in the bass clef and in the same range as the electric bass guitar. You can do further study on reading musical notes, and the bass clef in particular, by using any beginning Mel Bay bass book or even by visiting online teaching sites (see Resources).
Practice playing along with recordings of various styles of music that feature the double bass. This will help you get familiar with playing the instrument as well as help train your ear.