Audacity’s Envelope tool makes you a DJ

I recently had the chance to invite friends and family to a celebration, and as I was planning the event I decided I wanted music – both for ambiance, and for dancing – but I really don’t like hiring a DJ for these things. Aside from wanting to save money (which was a factor, of course), I’m not very fond of the emcee role that most DJs naturally take on. So I set about creating my own playlists for my iPod touch.

The playlist idea was shaping up nicely until I learned that my iPod touch, being 4th generation (I mentioned being careful about money, right?), did not have a very important feature: the ability to crossfade tracks. This is one thing that a DJ really helps with – getting rid of the pauses that come between songs. Some of those can be mitigated by going into the track info in iTunes and choosing specific start and end times for each song (very useful for songs that have ginormous gaps at one end or the other), but it doesn’t have that smooth transition that makes it sound professional. 

I decided that I could live without the crossfade for the ambiance music, but when it came to the “get everyone to the dance floor” tracks, I wanted songs to transition seamlessly so no one had to stand there awkwardly waiting for the next great beat to start up. I didn’t have time or desire to hunt down another way to play music, but I remembered my favorite tool in Audacity, a free audio-editing software program, and I was set.

What tool, you ask? Why, it’s the Envelope tool! Allow me to explain.

Audacity’s Envelope tool provides a way to adjust the volume from one point to another within a track. If you only have one track, that can be nice (imagine adjusting that really loud part of your favorite song so it doesn’t give you a heart attack each time it comes on), but not that earth-shattering. But if you decide to combine several tracks (think theme music transitioning to speech in a podcast or radio show), it can make that crossfade transition happen for you. The key, in my case, was to have all of my dance songs in one Audacity project, overlap the end of one song with the beginning of the next, and use the Envelope tool to transition.

To get my tracks adjusted and ready for the crossfade, I used the time-shift tool…Image of the Audacity timeshift tool.…and slid each successive track to the right until there was only a short overlap:

Image of two tracks in Audacity, with the second one's start time overlapping the first one's end time by a few seconds.

The Envelope tool is a little tricky at first, so it helps to have some guidance. First, click the envelope tool in the toolbar. It’s right above the time-shift tool.

Screenshot of Audacity's tool group, with the Envelope tool selected.

There are two main challenges with the envelope tool: placement, and adjustment. Once you have the envelope tool selected, you have to click inside one of your tracks to place it. The tricky bit here is that your first click to place the tool might change the amplitude (volume) of the whole track, so once it’s placed you’ll want to adjust as needed. For example, here’s a music track before adding an envelope: Screenshot of a music track in Audacity before placing the Envelope tool.

Now, note that the volume is reduced inadvertently when I add my first envelope: Screenshot of a music track in Audacity after the first Envelope tool has been placed. The Envelope tool is indicated, showing how the overall volume of the entire track is currently reduced.

To adjust the envelope, all you have to do is grab one of the controls (the white boxes) and drag up or down – or even side to side – if it’s not placed in just the right spot. The dragging isn’t so hard, but if you don’t grab one of the controls just right, Audacity thinks you really want to add another envelope, and if you’re not careful about how you click you can end up with envelopes all over the place.Image of an audio track in Audacity with too many Envelope tools added.

Oops. If that happens to you, see if you can grab one of your stray envelopes, and drag it off the track entirely before letting go of the mouse. The extra envelope should be deleted.

Ok, now for how to actually crossfade a couple of tracks. We’ll start with the track we want to fade out. Add two envelopes: first in the spot where you want the song to start to fade, and the second one at the point at which you want that track’s volume to have dropped off completely.

Screenshot of the two overlapping music tracks in Audacity, with two Envelope tools placed in the first track. The first one is placed at about the time that the second track begins, the second one is placed at the end of the first track.

Then, grab a hold of one of the controls in the second envelope, and drag towards the center. You can grab any of the four white boxes, but I recommend the topmost or bottom-most for the best control. Be careful as you drag the tool: if you let go when it’s smack in the center, you might have trouble picking it back up again. Here’s how mine looks when I’m done:

Image of the two overlapping tracks in Audacity, with the second Envelope tool in the first track now dragged towards the center of the track, allowing the volume of that track to drop off gradually instead of suddenly.

Now I add two envelope tools to the second track; this time, I grab the first one and shrink it towards the center, so it will start soft and gradually get louder. Here’s how they look when I’m done:

Image of the two overlapping music tracks in Audacity, with the second one adjusted to fade in as the first one fades out.

To listen in and make sure the crossfade sounds good, I prefer to change back to the selection tool first…Image of the Select tool in Audacity.…and highlight the crossfade area. Then, when I click play, I can focus in on the crossfaded area, or however much I want to hear at that time.

How long should the crossfade take? That’s up to you to decide, but I went with 3 seconds myself. I lined up all my favorite goofy dance songs one after another (including the much maligned Hokey Pokey, I freely admit), exported the entire project as an MP3 and saved it as “DanceMix” and we were good to go! Party on, Wayne!

Leave a Reply

Your email address will not be published. Required fields are marked *