Hello,
I’m new on this forum, I entered this page, because I use Audacity and I have a problem.
I recorded a concert of our band with my Zoom H2 and Audacity. For some reason the previous recording on my SD-card remained on the card, so now I have a wonderful concert with an annoying background voice of someone speaking. Is there a way to remove or reduce the voice in some way within Audacity?
Thanks in advance!
Berend
Are you sure that you have downloaded the files correctly from the H2?
Is the concert recorded as a mono, stereo or 4-channel recording?
Is the unwanted voice present on all channels of the recording?
I don’t own one of those Zoom recorders, but I’m not sure how that happened… It’s not easy to “accidentally” mix two audio files and I don’t think that recorder has a “sound-on-sound” feature… (It’s kind-of like superimposing two images on top of each other… It can happen with a film camera if you can somehow re-shoot without advancing the film, but it doesn’t happen in a digital camera where the two images are in different files.)
If the two sounds are in different channels, you should be able to mute or select one channel at a time. It seems more likely that the two sounds are on different channels (or tracks), and they are getting temporarily mixed in real time during playback… This is easier to do accidentally and easier to fix.
Or, if you happen to have an unaltered copy of the previous speaking-recording, you may be able to subtract it out. Let us know if you have the previous recording and we can help you with that. And if you do have it, does it line-up in-time with the mixed recording… It needs to line-up exactly.
If the two sounds are blended together, you won’t be able to fix it. 
Noise removal, only works on constant low-level background noise like hum or tape hiss. Other techniques such as filtering won’t work either since music and voice frequencies overlap.