Beat matching is the most basic form of mixing. It involves playing two or more records simultaneously and synchronizing their tempos using variable speed controls. Once the beats and phrasing of the two songs match, you can fade between the two or combine individual elements from each by using the separate equalizer on each channel. Generally, DJs play one record first and listen to the second through headphones as they sync it to the first. Recording and layering short sections of beat-matched records can allow you to "cut and paste" new original compositions. DJ Shadow, RJD2 and The Dust Brothers are examples of DJs that have practiced beat matching.
Scratching started in the 1970s as a flashy way for DJs to play back a second record over one that was already playing. Rhythmically moving the record back and forth, by manually placing the needle over the point where the first beat occurred, produced a "scratch" sound, allowing DJs to create patterns and phrases that weren't part of the original song. Scratching has developed a complex catalog of different techniques. Competitive scratch DJs, such as Qbert, Craze and Shortee, have produces instructional videos, explaining how you can recreate particular scratch sounds and how these can be chained into rhythmic musical phrases, eventually moving on to high-intensity improvisation.
Beat juggling involves taking two records, often two copies of the same song, and playing them in sync, as if beat matching them. By quickly rewinding and cueing individual beats or notes, its possible to reshuffle the sounds in a loop to give them a whole new feel. Solo drum loops are often used for this as they allow easy access to single drum hits. Beat juggling is considered one of the most difficult DJing techniques as it combines a number of advanced skills: rapidly cueing records very accurately, repeatedly switching focus from one turntable to another and making numerous edits and timing adjustments within each bar. DJ Shortkut and the X-Ecutioner's Rob Swift are considered masters of the technique.
Pioneered by The Scratch Perverts from the UK, wire tones occur when a deliberate feedback loop is created within the mixer, resulting in a heavy droning buzz on one of its channels. The buzz can then be rhythmically chopped into individual notes using the crossfader and manipulated with the equalizer. DJ Kentaro from Japan is a notable user of noise effects, placing strips of masking tape on records from the center hole to the edge. As the record rotates, the needle hits each strip of tape and produces a loud, low frequency "thump." By arranging multiple strips at different angles on the record, it's possible to create a repeating rhythmic pattern.