LS,
I have 2 (mono)recordings of the same concert.
These are old audience sources, not real good but also not so bad.
How can I mix in Audacity these 2 sources to create 1 stereo image?
Gr. pinkf
You can try importing each recording into a mono track, then selecting both tracks and right-click > Make stereo track
But unless you can get them exactly time-synchronised, and at the same volume, and the people recording didn’t move around, I don’t expect the result will sound good.
The time synchronisation is probably the most critical. If you need to shift a track you’ll need to do this on the mono track before merging.
Invariably, you are also going to find that one of the recordings will end a few seconds if not before the other. This can make listening a nightmare.
To correct for this, use Effect > Change Speed on one of them to match the selection lengths. Yes, there will be an imperceptible pitch shift.
Alternatively pick the best one & make a pseudo-stereo version of it.
There’s more than one way to skin this cat …
https://wiki.audacityteam.org/wiki/Nyquist_Effect_Plug-ins#Pseudo-Stereo
https://www.kvraudio.com/product/stereo-touch-by-voxengo
https://polyversemusic.com/products/wider/
I’m with Trebor… Pick the best recording and leave it mono or use a simulated/synthesized stereo effect. …I actually made a 5.1 surround track from a mono concert recording! I used a “fake stereo” effect plus I did lots of editing. I made separate tracks for the talking between songs and put that in the center channel. I “borrowed” applause from different parts of the recording and put that in the rear channels. The music in the rear channels was created from the “fake” left & right channels with a short delay and added reverb.
If you want to use one recording on the left and the other on the right the results could be “interesting” but you won’t get proper stereo…
The procedure would be to open or import the 1st track, then use File → Import → Audio and the second track will appear below the 1st.
At this point you still have two separate mono tracks and you can adjust/balance the volume independently.
You can also click & drag the track name above the waveform to move a track left or right to align them. (You’ll probably want to zoom-in.)
When you’re ready, click the little drop-down arrow to the left of the waveform and choose Make Stereo Track. (The top is left and the bottom is right.)
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Amplified live music is almost always mono (with the same sound coming from the left & right, or more, speakers). Professional live recordings are usually close-miced, multi-track recorded, and mixed for stereo (or surround, etc.).
For proper stereo the left & right channels have to be synchronized perfectly down to the sample level (i.e. At 44.1kHz there are 44,100 samples per second) and two different devices WILL drift out-of-sync. The odds are it will drift enough to get some “phasing” and by the end of the concert they might be far-enough out of sync to get an echo. (Slight timing differences can actually enhance spacial effects.)
And, the two microphones have to placed properly on the left & right, or with directional mics they can be located together and pointed left & right.
How can I use the wider plug-in with audacity?
I do not know how to install this plug-in.
Gr pinkf
Not finished yet : then you need to enable the new plugin via the plugin manager before it will appear in Audacity’s effect menu … https://manual.audacityteam.org/man/manage_effects_generators_and_analyzers.html
If it’s an orchestra I would use Voxengo’s “Stereo Touch” rather than “wider” plugin, (the latter can be electronic sounding).
Voxengo’s website is currently unreachable 
, but you can still get the plugins from the Waybackmachine …
https://web.archive.org/web/20170702110820/http://www.voxengo.com/files/VoxengoStereoTouch_29_Win32_64_VST_VST3_AAX_setup.exe