There are two kinds of drum loops: audio and MIDI. There are advantages and limitations to both. To use them most effectively one must understand what they are (and what they aren't).
An audio drum loop is a short recording of a drummer playing real drums, and it can be played as regular audio on any media player that supports the format it was saved in: WAV, MP3, etc. The recording generally lasts one to four measures. Both ends of the audio clip are precisely trimmed so that when played as a loop it sounds like a continuous rhythm. Audio loops can be inserted into any recording program as normal audio, and looped to create a beat.
A MIDI drum loop is not a recording at all. It is simply a stream of data, and makes no sound on its own. In order to hear what it's doing, the MIDI data must be read by a sound module, which will then produce sound by following the commands it is given. These commands include things like pitch, duration, volume, and so forth. When a MIDI drum loop is played through a drum plug-in such as Addictive Drums or EZ Drummer, the result is a drum pattern, which can be looped to create a continuous beat.
Now that we know what they are and how they are created, let's talk about the important differences between the two.
Audio loops can sound more like a real drummer, because they can be an actual recording of a real drummer, playing real drums. All the nuances and idiosyncrasies of a human drummer can be captured. Audio loops can also be recordings of drum machines, trash can lids, metallic factory sounds, or cows mooing in rhythm. The point is, they are real audio recordings. The disadvantage is that audio is much harder to manipulate than MIDI. It can be difficult to isolate and manipulate a single sound in the clip; a hi-hat, for example. It can also be difficult to get the rhythm to exactly match the beat of per-recorded tracks. Software for slicing and time-stretching audio clips is getting better all the time, but it's still a pain in the butt, and never sounds quite right to me.
MIDI drum loops, on the other hand, are easy to manipulate. It is simply data that needs to be changed. Most (and by "most", I mean "all") multi-track recording programs these days include a MIDI editor that makes changing drum hits a breeze.Want the hi-hat playing sixteenths notes instead of eighths? Easy. Want the snare on the up beat of "four" instead of the down beat? Piece of cake. The sound of MIDI drums is completely dependent on the quality of the samples in the sound module it is being played through. This is also a huge advantage of MIDI drums loops. Like the snare sound, but want a different kick drum? Done. Or a different low tom? Nailed it. Want a longer decay on the crash cymbal? Can do. A quicker gate on the snare? A cinch. A MIDI loop's biggest disadvantage is that it can sound mechanical. The quality of the loop is dependent on who programmed it.
Audio loops are best in situations where a continuous beat is required, such as dance, disco, or rap tracks. Different audio loops can be combined for fills or breaks, but generally speaking a drum track made of audio loops will stay substantially the same for most of a song.
If you need drums that play stops, punches, fills, complex breaks, or weird time signatures, MIDI drum loops are the way to go. Despite the moniker "loop" MIDI drums tracks don't have to be loops at all. In this medium loops only exist as a quick way to create a track. Once there, the "loops" can be altered, shortened or lengthened, merged, or cut to create whatever kind of drum track is desired.
The Bottom Line
90% of the time, when people ask what the "best drum plug-in" is, they are asking about sound modules that play MIDI drum loops. These include Steven Slate Drums, Addictive Drums, EZ Drummer, and many, many more. Most (and by "most", I mean "all") drum plug-ins come with a big collection of MIDI drum loops that can be imported into any recording program and played through the plug-in to create drum sounds.
And the best one? Steven Slate Drums, in my opinion. The interface sucks, but the sounds sit in mixes better than anything else I have tried. Want to hear them? Click on the "My Songs" button above and listen to Big Train, Madame Desire, or Ready for Country. Let me know what you think!