If you're musically inclined, or have an interest in how music is made, then there's nothing more rewarding than taking up the study of a musical instrument. Generally this will mean learning to play it! Many of us started upon an introduction to making music at school in our junior years. Popular instruments upon which to learn include recorders, harmonicas, simple flutes and pipes; and more intensively; piano, violin, guitar and cello.
So often people have an innate fear of picking up an instrument for this first time, on the basis that they think they'll never be able to play a note and could be the subject of ridicule. However a simple scale on a recorder can be mastered within a few hours - a few days at most. Everyone has to start somewhere! It's not at all true to suggest that the recorder HAS to be a simple instrument. In fact, it features in a few major classical works where variants of the instrument require serious practice and dexterity.
However, staying with the recorder, learning a simple scale will also effectively introduce you to the way in which music is written -- the language of music -- notes on staves of different pitch and duration. This written language is probably the most daunting part of the 'initiation' process, but as it's logical, and as you progress from very simple stages, you'll soon pick it up and after a week of practice, reading it will become almost rote. It DOES take a while (some musicians of the highest calibre never stop learning) but the rewards are great.
The chromatic harmonica or 'chromonica' is a nice instrument to start with. It has a useful pitch range (four octaves are available on some models) and simple melodies are soon picked up and memorised, although one should never discard written music while practising. If you think that maybe the chromatic harmonica is a little boring and has little scope for advanced playing, then I suggest you listen to Larry Adler playing with a full symphony orchestra!