All shows were produced between the late 1970's and late 1980's and were televised on The Children's Channel in the late 1980's/early 1990's. I have double checked old newspapers online to be certain of the titles.

The first show was called 'Make Music Fun'.

The second was an animation called 'Rootie the Pixie'.

The third , I have had more luck with. It turned out to be a Czech cartoon (in Slovak language) called 'Oranžová schránka'.
http://www.slocartoon.net/?main=cartoons/cartoon&cartoon_id=35507
This is very much available in its original language. I am, however, trying to ascertain in the English dubbed version 'The Little Orange Mailbox is available.

Any information on the existence of these shows would be greatly appreciated.