As technology modernizes, today's DJs have adopted different types of equipment to play and mix music. The traditional DJ used two turntables plugged into a DJ mixer to mix music on vinyl records.
Today, DJs specialize in high quality CD players known as CDJs, which were developed for the modern-day DJ. CDJs can take the place of turntables or be used together with turntables. Many CDJs can now play digital music files from USB flash drives or SD cards in addition to CDs.
Turntables allow DJs to play with vinyl records. By adjusting the playback speed of the turntable, either by adjusting the speed knob, or by manipulating the platter (i.e., by slowing down the platter by putting a finger gently along the side), DJs can match the tempos of different records so their rhythms can be played together at the same time without clashing or make a smooth, seamless transition from one song to another.
DJ mixers are compact, analog mixing consoles specialized in DJing, but most DJ mixers have far fewer channels than a mixer used recording studios or live sound events. The standard live sound mixers in small venue halls have 12 to 24 channels, and standard recording studio mixers have even more (as many as 72 on large boards). The basic, entry-level DJ mixer may have only two channels.