[Martha]

You could learn to read music just by singing. As HFWR says, learning some music theory is very helpful. Guitar and piano are good for learning music and learning chord construction. Piano is good because so many kids start music on the piano. Electronic pianos have come down in price over the past few years and don't take up the kind of room a standard piano takes. Plus, the different sound options make it fun to practice. (For example, you can sound like a standard piano, electric piano, pipe organ, etc.). I have been giving beginning piano lessons to some relatives and I have noticed that the adult piano books out there are pretty good at moving people along, not using totally stupid songs, and throwing in enough theory so you understand a bit about how western music is structured.

My first instrument was violin, so it is not like it is necessary to start on something like a piano but IMHO you can sound half decent on a piano far before you would sound half decent on a violin. Or a clarinet. Etc.

It is fun. Go enjoy yourself.