So I've taken up a new instrument: from the title you probably already guessed what it is. Fellow early music afficionados know the fiddle of which I write, but seeing as how the heyday of this instrument was about 3-4 centuries ago, the uninitiated might beg the question: what the hell is it? And why do you want to play it?
The easy question first: viola da gamba means 'viol of the leg,' as opposed to the viola da braccio, the 'viol of the arm.' So as not to expose my ignorance this will be brief: the violin (braccio) family became vastly more popular than the gamba family in the late 17th/early 18th centuries, because (among other reasons) they were louder and more suited to the big concert halls that began to develop at the time. Gambas were quite often played by amateurs in a consort (sort of a precursor to the string quartet) but a tradition of virtuoso solo playing did arise in France, primarily focusing on the basse de viole, which is actually the second largest member of the family (third if you count the double bass as a viol, which it could properly be considered since is sort of a hybrid with features from both the viol and violin families.) I won't go into much more detail; good ol' Wikipedia will tell you far more than you want to know about it.
To the why (and how) I can speak more properly. I had known of the instrument for a long time, but after watching the flawed but fascinating French film Tous les matins du monde (All the Mornings of the World), which was about two very famous gamba masters from the late 17th-early 18th centuries (Monsieur de Ste. Colombe and Marin Marais,) I was captivated by the rich, intense and intimate sonority of the instrument.
Being someone who plays a number of instruments but for the most part not terribly proficiently (i.e., enough to get by in a jam session and amuse myself and my friends), I've long wanted to seriously study another instrument. Many things factored in: I wanted to play something that was versatile, but could be played in baroque music (no clarinets or electric guitars, for instance), I wanted something that was primarily a line instrument (not focused on the 'vertical', but on the 'horizontal' aspect of music) and, having been a keyboard player my whole life, I'm fascinated by the concept of being able to alter the character of an individual note as it is being played. Playing the piano, once you've struck the note its pretty much done; your release, pedaling and other factors can change the quality of the note to a certain extent, but not the way, say a trumpeter or a violinist can radically affect every aspect of a given note simply because of the nature of the instrument.
So after pondering and dithering and vacillating for a few years, I settled on the viola da gamba. It wasn't until after I had really decided to go with this that I found out (fortunately for me) that the gamba is considered an 'easier' instrument (whatever that means) for an adult beginner; a quote I found on Wikipedia said something to the effect that this instrument heralds from a time 'when musicianship was valued over virtuosity,' (see the above link for the exact quote.) Yay for me; I accidentally picked an instrument that isn't considered prohibitively difficult to learn.
Not that you could convince me of that...I can occasionally get a reasonable sound from it, but mostly when I try to bow it the result is truly hideous. But more on that at a later date...