Welcome. I like your collection of melodicas. I see you have a Hohner 26. I don’t know if you have seen some of my earlier posts about the Hohner Piano 26s, 27s, and 32s, but these are special melodicas because the sound holes are on the bottom of the melodica. If you hold the melodica using the end opposite the mouthpiece, you can muffle the sound by holding the melodica against your stomach and chest. Then by moving, twisting, and waving the melodica around (primarily moving it into and away from your body, you can achieve significant modulation of the sound. The effects can resemble the sound harmonica players get when they cup and uncup there harmonica.
I am still learning how to do this gracefully and how to apply the techniques in my playing, by these melodicas really open the possibilities for expression.