Toletta de marteloio is a fancy way to say "hammered dulcimer," which is an instrument that you can play like a big xylophone!
Imagine a box that is kind of like a big guitar without strings. On top of the box, there are lines of metal strings that run across it horizontally.
Now, picture yourself holding two small mallets or hammers - one in each hand. When you hit the strings with the mallets, they make a sound! It's like playing a xylophone or a marimba, but instead of hitting wooden bars, you're hitting metal strings.
It's called a "hammered" dulcimer because you use the mallets to hammer or strike the strings.
And why is it called a "dulcimer"? That's because it's part of the same family of instruments as other dulcimers, which are usually smaller and have fewer strings. The word "dulcimer" comes from Latin and means "sweet sound."