The bass forms part of the rhythm section. This is a stringed instrument from the violin family that produces very low-pitched tones and is frequently played one note at a time. The primary role of the bass is to form the rhythmic pulse of the music.
Drums are percussion instruments, and they also provide rhythmic support for the music. They typically produce a regular pattern throughout the whole song.
Woodwind instruments form part of the melody group, and include saxophones, clarinets and flutes. These instruments primarily produce sound when a musician blows air through a reed. In the case of the flute, a sound is produced when air is blown across an edge. The melody instruments play the theme of the music and are accompanied by the bass and percussion, but can sometimes be used in the background in an accompanying role, too.
The brass instruments are also part of the melody group, and include trumpets and trombones. These instruments produce sound when a musician blows into them, causing air to vibrate in the tubes.