Tembro (which is Esperanto for musical "Timbre") is a virtual software instrument based on samples. All instruments are permanently built-in, there is no option to load your own files. New instruments are only added with new releases, old ones are never removed.
That makes Tembro reliable, predictable, portable and compatible. All projects and all users have the same "instrument" with the same instrument sounds, numbering system, midi controls… ; a solid basis for communication and collaboration.