Tutorial - Multi-track Overdubbing
Introduction
This tutorial describes a method of creating a multiple sound track overdubbing session using Audacity. You record one track then play it back and add a second track against it: drums, guitar, voice, other instruments or voices and repeat as needed.
With the methods described here you will be able to hear a mix of your live recording and the previous tracks simultaneously in your headphones. Live monitoring is often unavailable (or you hear yourself in the headphones after a delay) without hardware designed for this purpose.
The procedure is similar for any USB audio adapter, USB microphone or mixer providing that it has a headphone output and some way to mix the live signal with the computer playback signal and present that mix at the headphone output.
If your USB microphone, USB audio adapter or mixer does not have a headphone output you should follow the advice on Overdubbing using your computer's on-board sound card using the hardware you have on hand. It is strongly recommended that you do not use your computer's built-in microphone.
Advice on connecting and testing several specific hardware combinations are available at Recording multi-track overdubs with specialist hardware in the Wiki.
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If you have not yet made a recording and played it back using Audacity and your selected hardware, please read our First Recording tutorial. |
Hardware
You will need hardware that allows you to:
- Get sound into the computer
- Listen without a delay to the sound going into the computer (the live sound)
- Listen to the previously-recording tracks simultaneously with the live sound
Hardware that will accomplish this includes:
- A USB audio adapter
- A USB microphone that has a headphones output
- A USB headset
- A conventional analog microphone plugged into an external USB adapter that includes a microphone pre-amp
- A conventional analog mixer
- A USB mixer
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In every case the device must include the ability to mix the live sound with the previously-recorded tracks and present that mix at a headphone output jack. Most USB microphones do not include this capability. |
Almost any Windows, Mac or Linux machine with fast enough USB and good storage can be used. You will need headphones or earbuds. If you require cranium-crushing headphone volume you may need a headphone amplifier. You must get the headphone sound from the USB audio adapter, output on the USB microphone or headphone jack on the mixer, not from the computer headphone output. Headphone monitoring is good. Live microphones and speakers in the same room is a recipe for feedback.
First recording
First, make a simple recording with no overdubbing or other fancy tricks; your system must work correctly for simple recording and playback before we go further.
While listening to the playback of your test recording, talk into the microphone or play your instrument. You should be able to year your voice or instrument along with the playback. This demonstrates what you will hear during the overdub sessions; any combination of existing tracks will play in your headphones in addition to your live voice or instrument, allowing you to play along with the existing tracks.
If you cannot hear your live voice or instrument simultaneously with the playback you are not ready to begin overdubbing. This tutorial cannot cover every possible hardware configuration. If you need help, post a message on the Audacity Forum.
Setting the recording latency
Latency refers to the delay between the time the audio enters the computer and the time Audacity is able to record it to a track. For example, if you are recording a keyboard track, latency is the delay between the time you strike a key and the time that note is recorded.
For instructions on how to adjust the latency see the Latency Test page in the manual.
Performance
Choose (you do not need to save any of your tests). You are ready for your first overdubbing session.
Choose .
Confirm the following settings in the Transport menu:
- Overdub (on/off) is checked
- Software Playthrough (on/off) is not checked
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 a which can be adjusted with its control panel for rhythm and composition; it could be music from a rhythm and chord machine playing through a mixer.
If you are not using Audacity's Rhythm Track, be sure to record a lead-in—a non-musical rhythmical clue before the music starts which warns you of the imminent start. In a live band this would be the drummer or lead guitar count-in. You could use a synthesizer's rhythm stops or you can perform several rim shots into the microphone to establish the rhythm before the first note; tapping on the table with a pencil also works. You can edit it out later in post-production so nobody else will hear it.
Click the Stop button 
when you have recorded a sufficiently-long reference track then press the Home key.
Get ready to record your first real track, then click the Record button 
. You should hear your live performance and reference track playback in your headphone mix as a guide. Repeat for as many tracks as required.
The and 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 that can be set in Preferences. The gain control in the Track Control Panel to the left of each waveform controls the playback volume of that track—it affects the headphone mix.
When you get to a stopping point click the Stop button then choose to save your project.
As you progress, you should save a new Project periodically with a slightly different file name using . A good recommendation is to use ISO date and time for the file names or the start of the file names; refrain from using slash marks or other punctuation marks in a file name.
ISO Date and time
201110011500.aup -- that represents year: 2011, month: October (month 10), day: 01, time: 1500hrs.
Then save a new version of the song about every twenty minutes:
201110011520.aup
201110011545.aup
201110011602.aup
Do not go weeks with one Project and file name, and never cover up or record over existing work. If anything happened to that one Project, your project would be ruined and could nullify weeks of work. 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 project.
For extra safety it is good practice to periodically back up your project versions to a DVD-R or external hard drive for archive purposes. Remember that it is important to keep the AUP file and the _data folder together. One way to make sure of this is to create a zip archive of the AUP file and _data folder. In the unlikely event that the Audacity project is corrupted or your hard drive crashes you will be able to recover your work.
Note that Audacity projects cannot be played in computer media players nor burned to audio CDs. Export your project as 16-bit WAV or AIF for burning to a CD, or to MP3 for email or internet delivery. See Mixing for advice on doing the final mix of your project.
Troubleshooting
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- How much hard disk space do you have available? If your only experience with computer files is with spreadsheets, email or pictures live audio (and video) production will stun you with the amount of disk space it consumes. With high quality overdubbing, project files and folders get big in a hurry; with periodic saving of version of a project (as detailed above), a project can get seriously large.
- Communications features on newer Windows machines can cause unwanted changes in recorded volume or make the recording sound tinkly and/or hollow; see this FAQ.
- Always ensure that you are directly connected to a USB port on your computer. Connecting through a hub is likely to cause audio dropouts.
- Except in rare circumstances, you cannot plug a stereo analog sound mixer directly into a Windows laptop for recording. Mic-in (many times a pink port) is mono, not stereo, and too sensitive for the mixer. An external USB audio adapter neatly gets around that problem even if you're not planning overdubbing or complex production.
Synchronizing Tracks
Here are some tips if you're trying to record multiple tracks and synchronize them:
- When recording your first track, "count in" by tapping your microphone, pickup, etc... or import a count in from another file. Short, quick, percussive sounds at an even tempo is key here. Generating a click-track in a newer version of Audacity will work well, even if it is only a couple of measures.
- On all subsequent tracks, count in your rhythm, in synchronization with the playback of the first track's count, using the tapping method described above.
- You can now zoom in on your first track and subsequent tracks at the count-in. Pay particular attention to your last count-in beat (If you've counted in well, your last beat should definitely be in synchronization). Line up the beginning of the last beat in all subsequent tracks with the corresponding one from the first track, using the time shift tool.
- Your audio should now be synchronized. If not, adjustments should be minor, unless your count or performance was way off ... in which case, nothing can help you, except to re-record. When your song is finished, remove your count-in beats.
- If your tracks drift out of synchronization gradually, you may be having problems with skipping or with poor-quality hardware.
- You can always expect a small (but constant) time delay on subsequent tracks. This is due to fixed delays in the analog to digital conversion processes.
- To remove audio shifted before time zero:
- Ctrl + A to Select All (including behind zero)
- Shift + Home to move the selection start back to zero
- Ctrl + T to trim to that selection.
