I had a bit of a boo-boo when I recorded my little xmas project of "the First Noel" that is handy for showing a problem you can run into when recording. 

If you get a better mic for recording than the typical computer mic, they can be really great for catching subtle nuances of the sound of an acoustic instrument or voice, because even ones that are quite sensitive aren't all that expensive.  But every advantage has at least some possible drawbacks, and this is no exception.  The problem is that a very sensitive mic may also pick up sounds you didn't intend to record and that maybe you didn't even think was actually audible.

In this case, when I went to lay down the guitar and dulcimer tracks, I was using a simple percussion track as a click track that wasn't intended to end up on the final recording at all.  It something I worked up in 3/4 time with an acoustic kick drum sample on the downbeat and snare on the upbeats and a hi-hat ticking along marking 4 subdivisions per beat.  I was doing some fun tricky stuff with playing some notes on the accompaniment ahead and behind the actual obvious beat to get a more relaxed feel and a little bit of a certain sort of "swing" to the accompaniment to support the violin melody a certain way when I played it.  So I wanted all those parts clearly audible to me when I recorded so that I could get it just like I meant to, as a sort of rhythm skeleton.  But the problem would happen just as easy with a simple tick-tick type click track like we use for the group projects here.

It happened because I used some nice comfy "can" type headphones when I was recording the accompaniment tracks and I was within two feet or less from that nice sensitive studio mic I use for stuff like this.  And so it picked up the tiny bit of sound from the headphones themselves, without my noticing it right away.   I know it picked it up through the headphones and not through some software glitch, because the percussion/click track was being played on a different computer than the one I was recording on.  This kind of glitch often gets blamed on the software, but it is more often an actual audio problem like it was here. 

You can hear it particularly well in the quiet bit before the music starts where I have my voice cue and etc.  Not a huge problem there, since that gets trimmed off before the final mix anyway, but if you listen close, you can hear the occasional "boom" and "whap" from that percussion track all the way through the piece at certain moment. 

Now, there is an easy way to avoid having that happen on your own recordings.  If you use something like the little in-ear silicone earplug type things for being able to hear the tracks while recording, it won't happen.

I liked how the accompaniment tracks had gone down.  They had been "nailed it in one take" and I really liked the way the sound on them worked.  I didn't know how many takes it might need to get it that good again.  So I just decided to leave it as it was and hope it wasn't too noticeable in the final mix, since hopefully the listener would be focusing on the violin.  I had a member of my household with experienced ears fro sound engineering listen it through and they noticed the tiny bit of percussion in the mix but said it sounded intentional and they agreed to just let it fly as "good enough".

Anyway, to sum up.. You can avoid this sort of problem by using sound-tight earbuds, even if you do use a real sensitive mic and place the mic very close to get a good "intimate" sound.  It is easy enough to avoid, and could be a real pain to try to "fix" in a mix you're trying to get "perfect".  

If you listen close on some of the group projects here, you may also notice you can sometimes hear the click tracks.  That might be from a number of things, but one possible cause is some folks' headphones may be being just loud enough to being picked up when they record.