Not too long ago I had the pleasure of servicing a new Mason & Hamlin piano - their glorious BB model - a 7' grand piano with a bright, clear sound and prodigious bass.  A brief picture from my vantage point while tuning:

The owner, a gifted pianist and teacher, loves the piano and its clarity, but found it a little too bright and uneven in the upper midrange and lower treble, and wanted that brightness tamed and evened out, without losing the clarity.  A brief note: though Mason & Hamlins are indeed beautifully crafted and supremely capable instruments, I must admit that, personally, I prefer a bit of a warmer tone than the typical Mason & Hamlin 'house sound.' 

That said, my job is not to make the piano sound the way I want it to, but the way the customer wants it to sound (within reason - if the customer wants a sound that would require ruining a set of hammers, I'm afraid I'll have to raise a few objections!).  After all, I'm not the one who lives with the piano daily! If I were given carte blanche to voice the piano to my preference, I might go quite a bit further than the customer's preferences.  And while I might find the end result to my liking, maybe even ideal, the customer might find it comparatively dull and too mellow.

So with this in mind I set to work.  Voicing is one of my favorite aspects of my job - lots of pianos can be tuned impeccably well but still sound unpolished or even unpleasant if the voicing is uneven.  Voicing, when done properly, gives the piano an even, predictable and expressive tone across the entire keyboard and at all dynamic levels.  In this piano's case, the extra brightness was clearly noticeable but not aggressively so, and so it called for a light hand to eliminate it.  Particularly when reducing brightness, it is important to not attempt too much as the first step - you don't want to go too far and then have to bring notes back up that are now too dull. 

As a preliminary step in any voicing job, I play up and down the keyboard, and mark with chalk the range of notes that need to be addressed, and then in particular any notes within that range that stick out more than others (letting me know quickly which notes need more work than the baseline).  After this, I choose a few representative baseline notes (not the ones that stick out the most), lightly needle the hammers and put the action back in and test the result.  In this case, just a couple well placed needles per hammer were enough to get rid of the extra brightness.  After treating the rest of the hammers in the same way and testing, the brightness was gone except for those notes that initially stuck out the most.  A couple more needles per hammer brought those back into line, and from there it was just a matter of double checking for evenness with the rest of the range, making any small modifications necessary from there, and wrapping up!  The end result was a tone that was clear and even across the keyboard, and a happy owner!