In trance music you have a typical drum pattern that goes something like this:
Beat - |1---2---3---4---|
Kick - |X---X---X---X---|
Notice the kick hit on every beat?
And we already established that....
1 Bar =
1---2---3---4---
With me so far?
Now let's look at how we bring in the bass. The simplest is the "offbass" pattern which look something like this:
Beat - |1---2---3---4---|
Kick - |X---X---X---X---|
Bass - |--X---X---X---X|
This is how it will sound like:
https://www.youtube.com/watch?v=Lgs9QUtWc3MAnother common bass pattern is this:
Beat - |1---2---3---4---|
Kick - |X---X---X---X---|
Bass |-xXx-xXx-xXx-xXx|
The lower x is the lower octave note and the big X is higher octave note.
If x is A, then X is also A but it is play a bit higher. That's all to it.
This is how it sound like with this pattern. Notice the bass is very driving.
https://www.youtube.com/watch?v=zQqAWHcq81Q