Using more than one Playback Device

Audacity 2.0.3
Mac OS X Version 10.6.8

I have four independent click tracks that are necessary to coordinate a live musical performance. I need to find a way to play them back in sync and create four separate headphone feeds. I do not have access to a four-channel audio interface, but do have a two-channel audio interface.

I can play back the four tracks simultaneously in Audacity. I would like to send two of the tracks to the Built-In Output and the other two tracks to my two-channel audio interface. Is this possible? From what I can find, it only seems possible to send all four tracks to the same Playback Device.

I have created an “aggregate” device with the Built-in Output and the two-channel interface and set the Audacity preference for Playback Device to this aggregate device, but all four Audacity tracks are mixed together into one stereo output.

Is it possible for me to get two separate stereo outputs, or any other set of independent outputs, from Audacity? (If not, is there any other way to do what I’m attempting to do?)

Many thanks,


All Aggregate Device does is smash two devices together. Aggregate digital devices also tend to drift out of sync because the system can only use one of the two clock signals. Aggregate isn’t the gift everyone thinks it is.

Multi-track playback is notoriously difficult. I think the most convenient, commonly available method would be use the S/PDIF digital output of your Mac and connect a Dolby AC3 Surround decoder and amplifier system. I think Audacity with the FFMpeg software can create the 5.1 channel AC3 track.

Put the clicks on Left-Front, Right-Front, Left-Rear and Right-Rear. Ignore Center and Low Frequency Effects and Dial Norm.

Thanks, using a Surround track is a very interesting idea. We don’t have a Surround decoder available, unfortunately, or I’d give it a try.

I have been able to achieve what I’m after using Ardour and Jack. I got the idea here:

I assigned each click track to a separate channel of an aggregate device of Built-In Output and my two-channel interface. I understand, as you say, that these two devices will tend to drift out of sync. I’m hoping that since all I need is a headphone feed from each device, that any drift will not be consequential.