-- Hardware Overdubbing/Multitrack - Fake Overdubbing --



I'm going to describe a method of creating a multiple sound track overdubbing session in Audacity 1.3. That is, you record one track and then play it back and add a second track against it. Drums, guitar, voice. Repeat as needed.

This process uses your computer's built-in microphone and a pair of headphones.

You must be happy with not hearing yourself -- your live performance -- in real time in your headphones. You will hear all the previous tracks mixed as you wish, but your live voice or performance will not be in the mix until you finish recording and play the whole thing back.

You can use an old broadcasting trick of leaving one earphone off and cupping your hand so it forms a tunnel between your lips and your ear.

Including your live voice in the electronic mix on a home computer can be very difficult.



Almost any PC, Mac or Linux machine with a built-in microphone can be used.

I'm using my Mac earbuds for listening in this example, but nearly any good headphone or earbud plugged into the computer sound card will work.

I'm using Audacity 1.3.13. Audacity 1.2 is more difficult to use, is not well supported, and can be unstable.



We will do a simple recording. No overdubbing or other fancy tricks. The system has to work correctly for simple recording and playback before we go further.

Connect the headphones.

This is not a tutorial on making a simple recording and playing it back, but you need to be able to do that before you do anything else. There are multiple tutorials and wikis on Recording.

Audacity Manual
First Recording
General Workflow

Set the computer control panels, preferences and Audacity drop-downs to recognize the computer's built in headphones for playback and built-in microphone for recording.

Set Audacity Preferences:

Audacity Preferences > Quality > 44100, 32-bit Floating.
Audacity Preferences > Devices > Mono.
Audacity Preferences > Devices > Recording and Playback to the built-in sound devices.

Audacity Preferences > Recording (you may not have all of these settings)

[X] Overdub...
[  ] Hardware Playthrough...
[  ] Software Playthrough…

OK to close the Preferences panel.


Expand the sound meters by clicking on the right edge and drag to the right. The rest of the tools and panel graphics will move out of the way.

Click once anywhere inside the red recording meters to put them in Monitor Mode. They will measure the live show sound without sending Audacity into full record and wasting drive space. This may fail on certain linux machines using Jack.

Find your microphone. Scratch or tap around your computer until the red recording meters go sharply up. Some computers have it in the lid. Mine is in the grill just beside the left Shift Key.

Play or sing into the microphone. Adjust the Audacity recording control so you don't peak much over -10 to -6 on the Audacity meters. You can fix funny levels later, but you cannot fix overloading, smashing, and clipping (meters too far to the right).

Press Record. Audacity will take a second to configure itself and start recording. The blue waves will start to crawl left to right as you perform. Play or sing a simple song that you can use for rhythm and timing later.

Press Stop, Home. Play the track you just made. You should hear the track in your headphones.

This is all you will hear during the overdub sessions. You will only hear your voice or instrument in your headphones after you record it.



Home the cursor and Press record again and you will get a new recording underneath the first one. Sing or perform in time to the first track. Press Stop, Home.

The show will have two tracks, one from each performance, but it may be seriously out of time or rhythm -- even though you were in perfect time when you recorded it. This is Recording Latency and you can adjust it to zero using Audacity 1.3 Latency tools.

Done properly, both the live recording session and the playback later will be in perfect time.

File > Close > Don't Save


File > New

Generate > Click Track > OK.

Audacity Preferences > Recording > Latency Correction [ 0 ] milliseconds . . . > OK.

Play the new track and set the headphone volume so the clicks are very clear. Take off your earphones.

Push one of the headphones or earbuds against the grill where your microphone is.

Press Record.

Track one's click track is now being recorded onto track two through the headphone and built-in microphone. Good fidelity or volume is irrelevant.

Do that for five or ten seconds and press Stop.

Select the new track and Effect > Amplify > OK.

Put your headphones back on.

Play and both tracks will probably play out of step.

Magnify the timeline around one of the pair of clicks (drag-select and Control-E or Command-E.

Drag-Select the distance between the start of the click on the top track and the start of the same click on the bottom track.

That's how much the rhythm misses and that's the Recording Latency. Keep magnifying until you can get a good shot at accuracy. Control-3 or Command-3 to back out slightly if you magnify too much by accident.

Bottom of the screen > Middle Time Window > Length

Change the format using the dropdown menu to:

hh:mm:ss: + miliseconds.

You're mostly interested in the milliseconds -- the last numbers on the right. The difference between my clicks was 244 msec.

Audacity Preferences > Recording > Latency Correction [-244] milliseconds . . . > OK.

[X] delete the bottom track, put the headphone over the microphone grill again and press Record.

This time the two click tracks should look perfectly aligned or very close to it, and sound perfectly in time. If not, zoom in, measure the new difference and add or subtract that number to get the corrected latency value.

Before you get too obsessive about this, an orchestral musician once told me that the chances of any two instruments in the orchestra starting the same note at the same time is zero, so you don't need to adjust things down to the digital sample level. The latency values on home computers can wander in normal use.



[X] delete all the test tracks. You're ready for the first theatrical session.

The first recording can be whatever you're planning to use as a base, backing track, guide or rhythm track. It can be anything including Generate > Click Track which can be adjusted with its control panel for rhythm and composition. I used music from my rhythm and chord machine playing to the mixer. People have used existing sound files.


You should record a lead-in. That is, a non-musical rhythmical clue when to start before the music starts. In a live band, this would be the drummer or lead guitar count-in. I used the keyboard rhythm stops in my tests, but you can perform several rim shots into the microphone to establish the rhythm before the first note. Tapping on the table with a pencil works. Anything. You can sheer it off in post production later so nobody else will hear it.

Tick, tick, tick, tick, Music. Adjust as appropriate for music type and rhythm.

Stop > Home the cursor, press record and record track two using your live performance and track playback in your headphone mix as a guide.

The Mute and Solo buttons to the left of each track are valuable in overdubbing. Solo causes only that track to play and Mute turns that track off. Solo has options. The little volume control to the left of each timeline also controls the playback volume -- it affects the headphone mix.

When you get to a stopping point, press Stop and File > Save Project As. As you progress, you should save a new Project periodically with a slightly different filename. I don't use a kitchen timer, but I probably should. Being obsessive, I use ISO date and time for the filenames.


That's today at 3PM. October First, 2011, 1500hrs. If you glaze over at that, you can put dashes or underlines in 2011-10-01-1500.aup. You MAY NOT use standard date formats like 10/01/11

I will never duplicate a file by accident short of a typo. Do Not Use Slash Marks or other punctuation marks in a filename. I have to send work to many different computer types, so I don't use spaces, either.


New version of the song about every twenty minutes.

Do Not go weeks with one Project and filename, and never cover up or record over existing work. If anything happened to that one Project, you'd be dead and could take weeks of work with you. Think of what would happen if the lights went out right now, the computer ground to a halt and you were forced to use the last known good version of the show.

Audacity Projects are brittle, easily damaged and do not save UNDO.

Export to WAV for archive and Music CD, or MP3 for internet delivery or email. Do Not do production in MP3.

You may need to adjust the volumes and levels of the show so the Export doesn't overload.

All of the Audacity editing, filtering, and effects tools are available for each track or any combination of tracks before or after you sing/play. But not during. Audacity will not apply filters and effects in real time.



How much hard drive space do you have? If your only experience with computer files is with spreadsheets, email or Photoshop pictures, live audio (and video) production will stun you. Particularly with high quality overdubbing and UNDO, those project files and folders get big in a hurry, and with periodic saving, a project can get very seriously large.

Newer Windows machines in particular are openly hostile to entertainment production.
My music changes volume by itself and sounds tinkly/hollow


You can try to listen to yourself in the headphones by changing an Audacity setting. Audacity Preferences > Recording > [X] Software Playthrough (select).

Record a track with that setting. Chances are terrific that your headphone voice and your real voice aren't going to match. This is computer or sound channel latency and there's no adjustment for it. You should probably leave that setting deselected. But keep reading.


It's certainly possible to do a credible overdubbing job on a home computer with full monitoring, your live voice with existing tracks, by using specialty hardware or software only -- but the hardware needs you to write a check and the software can take very serious programming effort and some knowledge of how the inside of your computer works. If compiling binary libraries is too much for you and the hardware devices are inappropriate, you could always write a check to buy a commercial sound mixing program.

If no matter what you do the show sounds terrible or doesn't work at all, do drop in to the Audacity Help Forum where the elves and I will try to dig you out of trouble. Registration is required but free, and we may make you wait before your posting appears in public.

At minimum, you will need to tell us exactly which Audacity you're using, what kind of computer you have and which operating system. I use Audacity 1.3.13 on a Mac Mini with Snow Leopard, OS-X 10.6.8. Don't head straight to the details of the problem without telling us what you're producing and why.

Be prepared to tell us how the straight recording session went -- the one you did before you tried overdubbing.

Please don't post pages of diagnostic dump or error log unless we ask for it. If you do insist on posting it, use the [data] tags.