Can I turn a mono recording into stereo in FCP?
 

I went out today and took some footage stupidly with mono audio.

Is it possible to make this into stereo audio in FCP?

Nope. You can double your mono track and have it on both channels though, but that doesn´t make it a stereo recording.

well it's not really possible to make it into stereo in anything? The only thing you can do is maybe add some 'enhancement' that will fill the soundfield out a bit, but depending on the material, the results can be variable. The usual tricks are carried out in a dedicated bit of audio software rather than in an editor that has less complex audio facilities. Obvious additions are stereo reverb, leaving the mono original in the middle and adding a touch of stereo reverb. You can also split off the mono track, band limit it, and then add back a left and right with a short delay. This again gives the illusion of a wider soundfield - it is, however, a con of course. If the sound track has specific features in it - like maybe church bells in the background, you could filter these frequencies from the mono track and add these to one of the left or right channels - this then gives an apparent stereo shift when the bells dong - they come from 'over there' type result. another trick is to add subtle stereo pans like passing cars, or other background sounds on top of the existing track. These things can all work to some degree - but the original track is the key. Do you have any suitable software? Editors (and I'm not familiar with FCP), don't seem to have the ability to do these very small delays, being happy with 1/25 or even a 1/50th of a second, but tiny delays and other tricks are the fodder of proper audio editors. Sony Soundforge, Adobe Audition, Audacity and recording packages such as logic and Cubase all have the gizmos you need.

EDIT
Or did you just mean you have a single mono track and can't get it to appear on both channels? It suddenly occurred to me I may have missed the point and gone off one one!

My guess is that he only wants the mono track to be a stereo track, but not stereo audio.

It could be just copying the track and pasting into the other channel, if already set as stereo. Or it could be changing mono audio to stereo, using the single track on both sides.

But I don't use FCP, but as Matthias says, this should be easy to do. Perhpaps a post in the FCP forum, if no one knows the exact procedure in this forum.

If you just want to put a mono audio track on both channels, just open the audio track and CENTER the output slider between left and right pan.

Bingo. Mono audio centered to both stereo outputs.

And that setting can then be copied from the clip you've centered (select the clip and hit command C) - and pasted to any (or all) your other clips with the Paste Attributes command under the edit menu.

Hope that helps.

Possible with Soundtrack Pro
 

If you have Soundtrack Pro, which is included with Final Cut Studio, you can take a mono audio track and an effect gives the track a little stereo presence. Works OK.

Pan right/left
 

FCP will allow you to copy/paste another audio track. Then select the first and "pan left" and the second and "pan right." Finally, select them both and make them "stereo" which will link them together when you make level adjustments. Hope this helps.

One trick is to make the left track and EQ it wildly. Copy the raw track to the right. Copy the left track to the right and subtract it from the raw one (flip the phase of the EQ'd copy). You'll now hear some stereo spread. The EQ effects cancel one another if/when you go back to mono. You can also add different reverb to the two channels, but be aware that things don't cancel as perfectly. Slipping one channel (adding/subtracting delay) is another fun trick.

This is helpful when recording a vocalist playing guitar with only two mics (one on the guitar, one on voice.) Leave the voice in the center. Spread the guitar with the above tricks. It can give a nice, full sound.

You can simulate stereo better than you can record it IMO.

Create a duplicate L&R track. You may already have this. Just pan volume between the L&R tracks at the appropriate time (i.e. different person speaking). Layering the audio also helps. If you have another cameras audio to use, I would add that in another syncronized track to add depth.

If you can add some slight delay (a few ms) and some EQ variance between the left and right channels, it will also add to the effect.