The problem you’re talking about has to do with placing. There are several techniques for dealing with it. One is to place in sequence. That means placing only one note at a time ahead of the note you are playing instead of placing blocks of three or four notes together. You can even place in sequence on rolled chords.
Another technique, which should always(ALWAYS) be used is to place at exactly the same time as you play another string, thereby camouflaging any sound from placing. The third technique is to replace quickly and firmly onto the string, so that you stop quickly any sound that it can make.
I don’t know what level you are playing at, but you can and should practice these techniques, individually and then together, on much easier pieces than you are used to playing, or on exercises. If you practice them enough, you will develop muscle memory for these techniques and it will become completely natural.
Maria- Any advanced harpist does this, at least from the French school. There’s a video on youtube of Catrin Finch playing part of the Goldberg Variations. She’s doing all of the things I mentioned, but its very fast so it may be hard for you to see. Sylvain Blassel also plays parts of the Goldberg variations and you can see it there too. Particularly at the 3:50 mark on the video where there are some close ups of his hands. Emmanel Ceysson plays Une Chatelaine en sa Tour and right at the beginning there is a good close up of his hands.
With all of these players, notice that they never have more than 2 fingers in each hand on the strings at a time. They “walk” over the strings, or place in sequence as I call it. With all of them, their left hands are constantly muffling individual strings as they play. You can see the 3rd or 4th finger reach out and touch a string to muffle it as they play, and the muffle occurs at exactly the moment that they pluck a string.
William- I think Sylvain is an elegant player too. I’m planning to be in France and England this summer, and one of the things I want to do is track him down and meet him. I noticed when I watched his video again this afternoon that he also has some interesting fingerings in both the left and right hand that allow him to muffle individual notes with either hand. Its rare that you ever do individual finger muffles with the right hand, but he does that towards the end of the video.
I just looked at Sylvain’s video again and caught something else. Watch his left hand from the 2:10 point of the video. He muffles ever single note that the left hand plays, sometimes with the left thumb(in the descending scales) and other times with the 4th or 3rd fingers. In the rest of the video, he only muffles left hand notes when the harmony changes. When the left hand is playing notes that outline a chord, he lets them ring. This tape is a superb lesson in muffling.