I have been playing harp for over 50 years and have experimented with many configurations, trying many models from different manufacturers.
I now have the best sounding, easiest to play, fun harp.
The only thing I discovered that made a significant improvement in tone, warmth, clarity and fullness, air tightness and most importantly- ease of play was Tom Halchak 's
,Blue Moon Harmonicas, recessed brass combs for $64.95 for my Special 20.
I have been gigging with them for 8 years. I thought there was nothing more to be done.
Recently, I tried powder coated cover plates from Tom for $25.95 a set. The covers make the tone even warmer and fuller. They are smooth on the lips and will not rust. I like the different colors for identifying the right key in dark clubs.
(Tom also has these brass combs and plates for some other harps and manufacturers.)
These are true lifetime instruments!