Beatmixing is a technique used by DJs to seamlessly mix two songs together, allowing one song to end and another to start without a gap. This is achieved by altering the speed of the second record so that the beats are synchronised with the first record.
If the tempo of the second record doesn’t match the tempo of the first record, it’ll drift out of time, even if it was started in sync (shown below).
If the tempo of the second record does match the tempo of the first record, it should stay in time indefinitely (shown below). Some minor adjustments might be required for long mixes—commonly known as “pushing” and “pulling”.
Once you’ve mastered beatmixing, key mixing should probably the next port of call on your journey to becoming a superstar DJ.