I am attempting to convert many thousands of vinyl albums into MP3s. In order to speed the process up I tried to record via USB in one window, and edit, label, and export from a second window in audacity. Starting playback on this finished recording stops the recording left in the background. Can this be done? -Frisco 2.0.3
Audacity will not run two different instances of itself.
Koz
You should not be directly converting to MP3. You should export from Audacity in high quality WAV and use that for archive and production. Then use those to create the lower quality MP3 for your personal music player or other uses. If you have an option, listen to the WAVs.
MP3 always creates compression sound damage and you can’t stop it or fix it later. Audacity will not edit an MP3 without additional sound damage.
Koz
Just to clarify that a bit.
Audacity can have more than one “project” open at a time, but there is only ever one “Audacity” at a time.
In short, you can’t be recording in one project while playing another project.
Which isn’t strictly true either.
On Windows, a plug-in can play the current selection:
I start recording (wasapi loop back) in one window.
You hear the instance when I change the window per alt-tab and start playing the chirp per plug-in.
It is a “Loop Preview” in this case, i.e. the last second of the selection is played, followed by the first second.
The preview (for e.g. normal playback of a whole selection) can anytime be stopped by cancelling the effect (pressing enter or space).
However, this is only a proof of concept and probably not very convenient for you.
It actually depends on what you want to do during recording. You can’t for example not define labels on the fly, only control if they are placed correctly.
Also, there’s always the danger that you accidently hit space out of habit and your parallel recording would instantly stop.
My advice therefore, make the edits after recording.
By the way, you can place labels during recording (ctrl-m).
If we are being “strictly accurate”, that isn’t Audacity playing - it’s Nyquist playing. 
Actually you can 
As I discovered while doing some multi-project testing I found that I could run Audacity on two separate user accounts simultaneously and the each appears to operate completely indecently. Just this morning I was using one user account to play a recording from last night while using a second user account to use Audacity to create images for the Manual. I’ve even managed to record simultaneously on two users accounts, one recording WASAPI loopback to record the webstream playing on the computer and the second to record from my FM tuner and external USB sound card. 
WC
For now the best solution is probably to use some other application to record while you edit in Audacity - if you accept the risk that running effects in Audacity which could have high CPU usage or high memory usage (some Nyquist plugins) could cause dropouts in the recordings.
Gale