And yes, I used to DJ.
I also used to play the Alto Saxophone and I do lots more.

There are a few varieties of turntables.
There's the analog turntable that uses vinyl discs (piring hitam)
Then there's the CDJ that uses CD and sometimes have usb ports.
Lastly there's Controllers, it needs a computer to run, and only uses music files from your library.
Nowadays people usually buy controllers due to it's size, weight, price and it comes with multiple functions as awell.

It's basically just beatmathing, beatmaching is done either by manually or computerized, in the old days I'd count the beats and adjust the speed of my music to match the next song I'm lining up.
To manually count bpm (beats per minute), you can either;
1. Count all the beats for a full minute.
2. Count the beats for half a minute.
3. You get the idea.
Then if you counted for a full minute, you have your bpm, if half a min you multiple it by 2.
You will have roughly +/- 1 or 2 bpm difference.
It'd shorten the gap and save you time to adjust that rather than not knowing the bpm at all.

Now there's computerized bpm reads, and it can give accurate and fast readings.
There are lots more to this, such as harmonizing your tracks and choosing the right tracks to line up.

And yes, I used to DJ.
I also used to play the Alto Saxophone and I do lots more.

And yes, I used to DJ.
I also used to play the Alto Saxophone and I do lots more.