What you will find
Guitar loops are short performances recorded to a tempo: a funk lick, a strummed chord progression, a lo-fi jazz phrase or a washed-out ambient texture. They are a quick way to bring a live instrument into an electronic or hip hop track. Free ones come from community uploads, Creative Commons archives and producer packs given away as samplers.
Fitting a loop into a track
Start with the key and tempo on the card, when the source states them. Loops in a minor key usually work over a track built on the relative major too. Roll off the low end below about 100 Hz to leave room for the bass, and carve a little space around 2 to 4 kHz if a vocal sits on top.
Guitar loops often contain a recognisable riff, which matters for licensing. A loop from a community site is only as clean as its uploader’s rights, so the verdict on each card treats uploader-asserted licences with care.