Sonar has a unique feature that is one of the coolest ways to take music loops and make them your own.
Cyclone would easily win the "Most ignored Sonar feature ever" award in my book.
Take a music loop, Press Cntl+L to groove clip it.
Drag it into Cyclone and start redistributing the audio slices around the pads. Then set the loop points to create new timings and repeats.
Drag in a couple more groove clips and keep going. You will soon be twisting those looped cliches into alsorts of new directions.
Once you have something interesting, start putting pitch markers in the timeline to create an arrangement.
I cant understand why Cyclone has been left to rot. i cant find any other tool that does what it does.

PilotGav
It was asking HOW they're used, and how music today is produced as opposed to how it was 30 years ago.

In addition to what I mentioned previously about my use of loops, which resembles musique concrete more than anything else...
 
Songwriting "placeholders." I have a folder of what I call "placeholder bass loops." They are the most neutral and boring bass parts you'll ever hear, but they hold down the low end until the real parts come along.
 
Sonic seasonings. You have your track recorded, and a nice little djembe loop (or of course, one of the "Beat Filter" loops from my AdrenaLinn Guitars library ) can add the requisite ear candy so your music doesn't sound like everyone else's - especially if you slice and dice it.
 
Re-creation. Most of the loops in Hardgroove's bass loop library are variations on his original loops. One reason why they work so well in songs is because the variations have a certain consistency, but can be sufficiently different to stay interesting. A little cut and paste, and you can end up with a part that Brian played, but which he never played 
 
Inspiration. I'm editing a loop library of "rock anthems" from a guitar player who played with David Lee Roth and Sammy Hagar, and the guy can just churn our riff after riff. Almost every one of them makes me want to write a song around it...of course a loop is just one element of a song and I have to fill in the rest, but from that seed something cool and original can grow.
 
Audio for video and commercials. We're always last on the food chain and the budget is shot by the time they get to the soundtrack. With loops, you can do beds and music to support videos really fast. They never know the difference anyway, all they care is whether it supports the visuals. Many years ago I scored two movies using only Sony Acid and loop libraries. Took me less than a week per movie. I've also used loops for radio spots and such.
 
MIDI baseball cards - trade 'em with your friends. Several EDM artists trade MIDI loops because it's so easy to change sound, key, and tempo to fit a particular piece of music.
 
Recyling. So the rhythm guitarist played several really great bars in the first verse, but then ran out of gas in the second verse. Loop the best measures in the first verse, use them in the second verse, then do some editing to add variations.
 
Raising blood pressure. If you know a musician with excessively low blood pressure who hates loops, go on and on about how great loops are, and how you use them all the time. The other musician's blood pressure will rise to acceptable levels.

PilotGav
For example - musicians use samples and loops. No harm no foul... but when thousands of musicians are buying the same loops, sample packs and soft instruments... what's the point?

I was in a local blues bar a few months ago. Mostly for the food, but anyway. The band came on, and started playing. And it was a 12-bar blues song. They played, and every single part of that performance was predictable, because that's what the song structure requires. The lyrics may differ, the bass and drum fills might alter a bit from player to player, but really there's not much variety from song to song. Yet people love that and think of that as 'real' music.
 
So we see that giving people real instruments and getting them to play them manually is no guarantee of originality or variety. We also see that it doesn't really matter to the listener as long as they're hearing what they want, or to the performer if they're playing what they enjoy. And I think 'real' musicians often start drinking their own Kool-aid and saying things like "the tone is in the fingers" (no, it is not, and it is trivial to prove why the majority of the timbre comes from the rest of the signal chain) to pretend that human-performed music on physical devices is somehow intrinsically more diverse than computer-performed music, even when those humans are slavishly recreating the same style that existed 50 years ago.
 
As for the other side of the equation, i.e. whether it's possible to get great variety out of the same loops and sample packs... certainly. Give me 10 drum loops, 10 chord/pad loops, and 10 lead loops, and that's 1000 permutations. Do that again for a second section and you have almost a million possible ways to have arranged those 2 parts. And that's before you consider that usually the percussion part will be formed of 3, 4 or more separate loops, that the parts might be edited or have automation to change them significantly, that they may be pitch-shifted to create different chord sequences, or - and here's the shocking bit - someone might actually play a real instrument and put a completely new melody over the top of the loops. ;)
 
You also suggested that soft instruments are somehow a limit on variety... but I think you know, when you think about it, that's not the case. Soft instruments are an order of magnitude more versatile than physical ones because they're not constrained by needing to fit in a room, needing to be playable by a human, needing to be cost-effective to produce, needing to be made out of real world materials, and so on. I have VSTis of pretty much every tone and timbre. And I have soft synths that give me access to real instruments I will never be able to afford and will probably never see in person. That makes my music more diverse.
 

So I guess what I'm asking is where can I learn how all these factors... loops, samples, etc. are used today in order to produce fresh original music? What's the process? What's the secret?

 
I think the process is to use them as scaffolding for songs. You can plan out the basic structure of the track with loops alone and add to or remove them as necessary. And don't forget the power of editing and automation to change the character of the loops.

Kylotan
I was in a local blues bar a few months ago...

Your post has an extremely high wisdom quotient. Well done.

Anderton

Kylotan
I was in a local blues bar a few months ago...

Your post has an extremely high wisdom quotient. Well done.

I agree.  I need to order some loops and MIDI clips and quit whining about there being nobody around to collab with. 

Here's a little vid on it that shows spicing up a percussion track.  
https://www.youtube.com/watch?v=WwzINWSbrYk

This has turned into a really educational thread for me and generated some ideas. Over the weekend I was going through my music library and managed to find 1 record that has a rap/dance feel to it. Todd Rundgren's New World Order. I've been listening intently to it and find that he's done exactly what Craig and others have been talking about. All the pieces start with a looped groove and then he just takes it into a frenzy. I suggest folks that are behind curve (me) give it a listen to see what a rock/pop master can do with them.

True story:
 
After Apple pulled Logic from store shelves, a GC employee was grousing to me about how they had now been instructed to push Ableton Live. "But I'm a guitar player, I have nothing to do with loops."
 
So I said "Hum me the first two bars of 'Brown Sugar.'" He did.
 
Then I said "Hum me the next two bars of 'Brown Sugar.'" He did.
 
Then I said "Hum me the next two bars of 'Brown Sugar.'" He did, and got the point.
 
I concluded by saying "Do a find-and-replace with the Live manual and replace every occurrence of 'loop' with 'riff.' Then it will make sense to you." And it did 
 
(Not to give too much of a plug, but if you want to hear loops blended with rock music as well as electronics, there's my YouTube channel. All the songs, except for the live recording of Ambience Rose, have loops in there somewhere.) 
 
 

Another true story:
 
At one point I was spending a lot of time in Germany playing concerts with Rei$$dorf Force and Dr. Walker. But it was a helluva commute from Florida. So I created a loop library of my playing, and sent it to him so he could load me into his MPC and have a "virtual Craig" when I couldn't make the gig. (That library became the basis of the AdrenaLinn Guitars loop library.)

What/where is this famous AdrenaLinn loop library you keep talking about?