Combining loops using timestretch
One of the most creative techniques in sequencing is to combine two drum or percussion loops together. The results can be unpredictable, but that unpredictability can spark off further creative development.
Load up the two loops you have chosen onto two tracks of your audio sequencer. Unless they both happen to be the same tempo, one will be shorter than the other.
Assuming that the longer of the two loops is going to be your 'base' loop and is already at a suitable tempo, time stretch the second loop so that it is of the same duration.
Some time stretch software makes this easy. Otherwise you will have to work from first principles, which isn't a bad idea as familiarity with the foundation techniques of music technology will make you more fluent and comfortable with advanced processes.
Start by measuring the duration of the first sample in samples. (Seconds and milliseconds would do, but it makes the calculation more complex). Your audio sequencer will almost certainly have a 'get info' tool, or you will be able to measure it on the timeline.
Let's say it comes out at 150,000 samples (but it is unlikely to be such a nice round number).
Now, your timestretch software many allow you to enter 150,000 samples as the 'destination' duration of the sample. If so, easy peasy.
If not, then you might have to measure the duration of the second sample. Let's say it comes out at 110,000 samples.
Now you can apply a timestretch percentage, which would be 150,000/110,000 x 100 = 136% (136.36% if your software allows such accuracy).
The result will be two loops of equal duration which will both cycle smoothly (assuming of course that they were correctly trimmed in the first place, but that's another story).
Sometimes, it must be said, nothing useful comes out of this process. But other times you will be amazed at what you hear. It is well worth a little trial and error to end up with something that it is almost guaranteed no-one else has ever heard before.
There are of course other ways to achieve this...