conforming to time signature rules to make musical sense
The records that a DJ plays all roughly follow the same musical rules, in dance music they are usually arranged in four-bar phrases. Even if you are able to beatmatch, you cannot necessarily DJ effectively, and your mixes may struggle to make musical sense. When mixing a DJ needs to match up records phrases as well as their beats.
Counting Beats, Bars and Phrases
Before matching phrases, a DJ needs to be able divide a piece of music into beats, bars and phrases. The best way for you to learn this is to practice counting these musical elements every time you listen to a piece of music, whether it be trance or a dance pop record.
Now that you can count beats, begin to count each beat as a group of four. The majority of dance music is '4/4' time e.g. each group of four beats is a bar and can be counted as follows1,2,3,4 - 2,2,3,4 - 3,2,3,4 - 4,2,3,4 - etc, etc.
As a DJ you should count music in four-bar phrases, although they may appear to be longer than this (i.e. a four-bar phrase repeated twice to make an eight bar phrase). After every four-bars in a piece of dance music you should notice a small change in the sound, for example an off-beat drum pattern. Similarly after every eight bars, a larger change will occur in the sound such as a cymbal crash. These changes are markers which kind of represent full-stops in music, marking the end of one phrase and the start of another.
Matching the Phrases
When a DJ mixes they must be careful not to muddle up a records phrases with the phrases of another record. Even if both records are playing at the same speed they will not sound right if the phrases of the records start and stop at different times.
When beginning to mix a record into one which is already playing make sure the beat you have cue'd up, (see cue'ing up section) is the first beat of a phrase. Also you must start to mix in the second record at the first beat of a phrase in the first record.
Use Phrases to Help your Mixing
I have already mentioned the markers (changes) in a record which inform you of when one phrase ends and another begins. These markers are useful as prompts so that you know when to do something in the middle of mixing two records. For example, after a marker you may wish to move the x-fader a step across, increase the volume of the incoming record or swap the bass between the two records using the EQ (equalisation) controls on your mixer.