I wasn't sure if the OP were a musician, which is why I answered like I did.
Me too... I have often found (and was taught) that listening to the bass can be an easy way to identify the key and / or changes, since the bass is usually hitting single notes and they're usually the root of the chord. Of course, the melody often follows the same guidelines, so that makes sense too!
Originally Posted by author
If you're a musician, I guess you just listen to any part. Though bass is the last thing for me... heh
What is PROBABLY more important for you, if you want to cover those songs, is the range of your singer, and / or any conflicts with instruments like needing to be tuned down to do the same chord phrasing.
I'd start with that, and you will end up with the right key for YOU doing the song... which will sound better than your singer struggling and not managing to do the right key for the original artist.
This is not quite what the OP had in mind but CLAM Chordatea is an enormously interesting and potentially fairly useful little free, open sourced program that will analyze audio files (wav, mp3, etc, but not all formats) that you feed in and give you an ongoing readout of its analyses of the chords. It's not going to give you accurate readings of tricky jazz chords, by a stretch, but it will usually get you into the ballpark.
It's not a well-rounded commercial program but it's awful darn cute...
If you Google "guitar" and "tabs" you'll find a bunch of sites with guitar chord charts for popular songs. They're usually throwing in a few wrong chords, but at least they'll start in the original key.
you can cover any song you want find in what key you sing your best, if it`s not the song`s original one, transpose the chords and there you go. You don`t have to play covers in the same key they were recorded, play them in the key you give your best vocal performance.
I like to usually play from sheet when I am bored and for pop songs a huge number is simply in C major, quite a lot are in G or D major (lot of pop-folkish type, irish type..) and some are in F major then bit few in A major.
The rest of keys is not very typical some totally untypical (unless you are freddy mercury) and for most amateurs also very hard to play so they get quickly transposed to playable key.