Have an acoustic guitar audio track - caught thumb pick and want to eliminate that twang that is present for a few beats.
 
Are envelopes the way to go?  I watched a vid and know I can create them - I'll copy the clip before I work on it to hone my skill.  But, is that the peferred method or just 'a' method?
 
Don't really want to try punching or anything.
 
Thanks.

I'm not sure I understand your description correctly, but if that twang is ringin upon the rest of the picking/strumming, it will not be easy to clean it out. It might be impossible. What kind of envelope did you have in mind? I can't imagine solving this with volume or EQ.

If it's a lonely twang, then a simple volume envelope will do. Or you could as well edit the audio itself and get rid of the twang for good, not just mute it. 

Ah yes, I see.  The unwanted twang does ring and fade away, but other guitar notes/audio exists during that time too.
 
I was thinking there was a way to isolate that particular sound or frequency - like I had seen in vids where a Transient Shaper (I think) was used to remove unwanted freq from drums.
 
Or, I thought maybe I could select the clip where this is happening and just reduce the waveform (with an envelope?) and see if that worked.
 
Learn a new method/tool and maybe get rid of the mistake too.
 
It's a repeating musical phrase so I can copy from elsewhere in the clip if needs be.

The only sure fire way is to re-record part of it, either by punching in (preferable) or on a new track where you can fade out the old one & replace it with the new one for the duration of the "ring" and then reverse the fading.

Or find a section of the song where you're playing the same thing, split it at either end of the "good" part and paste it over the wrong bit.

Yep.  I copied a piece of the audio clip from earlier measure after reading Kalle's post.  Not perfect, but it will do.
 
(Topic for another thread.  I thought I could somehow use Audio Snap to line up the copied clip with the existing one using transient markers in both clips.  But Audio Snap remains mysterious, and I read here that it doesn't quite work that way.  I'll save that subject for another time.)
 
Thank you.