FL Studio is half-decent at exporting seamless loops when you’ve got the render mode set to “Wrap”. I say half-decent because while it will account for delay or reverb tails, it seems to have trouble with the release phase of instruments (audio)
Here’s a pretty straight-forward technique I’ve come up with to get around this. (In my case I’m using an older version of Sound Forge but any decent audio editor should do)
Step 1. Export what you want to loop, plus a tail of the same length (audio):
Step 2. Load the file in your editor
Step 3. Select the second half of the wave. In Sound Forge I do this like so:
A. Double-click the loop point that FL added to the wave:
B. Set the “Input format” to “Measures & Beats”:
C. Change the selection from 16 to 8 and click OK:
D. Double-click the second half of the wave
Step 4. Cut the selection
Step 5. Paste the clipboard at the start of the wave in “mix” mode:
Et voila!