• Add Complexity to Your Synth, Guitar, or Rhythm Parts
The most obvious use for delay is to add interest and rhythmic motion to a part. If your delay allows you to enter dotted note values, try setting it to sync to dotted 1/8th notes. Play a simple, synth part of straight, percussive 8th notes and listen to how much more complex it sounds. Try using delay on some things you might not think to ordinarily, such as your drum buss.
• Exaggerate the Stereo Sound of a Part
If you have a delay that allows you to adjust the delay rate down to the sample level (like Logic's built-in Sample Delay), offset one side between and 300-1000 samples from the other. You should notice the part sounds significantly "wider". This sounds brilliant on strings and pads, and can really add some sparkle to vocals. It also can help a part that's getting lost in the mix to stand out.
• Create Resonating, Metallic Effects
On most delays effects, if you set the delay time to a very short value (50ms and below), and turn the delay feedback up (not TOO high, though or your ears are going to be REALLY sad), you can create "robotic" type effects with an old school vibe. You can use it to recreate the fake vocoder sound on lots of old school rap and electro tracks if you send speech through it, and if you mix the effect as a send effect, it can add a harsh, metallic sheen to snare drum or other percussion tracks. If you play around with this effect, you'll notice that you can "tune" the effect by tweaking the delay time. If you're so inclined, you can try automating the delay time to follow the chord progression of your song. Most delays will glitch a bit when you try to do this in real time, so the best option is to render the track to audio and edit out the glitches by repeating an earlier region.
• Wash It
One thing ambient masters like Brian Eno or Robert Fripp discovered early on was how adept delay was for creating, giant sounding washes of sound. Try setting your feedback level fairly high, set your delay time to 1/4 notes or longer and play some chords with a lush pad sound and listen to how much thicker it sounds. Better yet, try setting up 3 or more delay effects in series, each with it's own delay time and feedback levels. This sounds great with stereo "ping-pong" delays. Even try setting up other effects before or after the delays. One of my favorite effects in Native Instruments' Guitar Rig is created by splitting up the signal and feeding it through delays, some of which have been pitch-shifter upwards. Try using a tape delay that degrades the signal with each repeat to dirty up your track and make it sound more organic. Also, try setting a reverb after your delay to create even more atmosphere. This way, you're applying reverb to each repeat of the delay in addition to the main sound itself.
• Bait and Switch
One cool effect that can add interest to a track is to record a part twice, using different sounds each time. Leave the "main" track dry, and then send the second track completely through a delay effect with the wet level set to 100% and the dry level all the way down. Mixed properly, the effect is of the second track being the echo to the main track, but with the different timbre of the second track, it can sound a lot more interesting. Try it with snare and percussion parts, too.
So what are your favorite ways of using delay? Join the conversation in the comments!