[X4U] Waveform Sound Editor

[Neil]

I'm looking for a waveform sound editor.  My needs are simple, mostly  
just cutting out unwanted sections or fading out.  I occasionally  
might want to join two different clips together, so a cross fade would  
be nice too.  I used to use the free version of ProTools back in the  
1990's.  That was plenty powerful for my needs, although these days it  
would be nice for an app to be able to edit MP3 files too.   Any  
suggestions?  Thanks.