There's a balancing act here between having an interesting role in the orchestra and having an interesting solo repertoire available.

In the first category, it always seemed to me that a lot of fun was had by the tuba section. String bass would be another good example, and you could branch out to jazz. Both of these are fairly in demand as far as I know. On the down side, your entire block will know if you are practicing the tuba and it's no small feat to carry it around.

Personally I went the opposite route and chose the flute. Flutes have many advantages, from being reasonably melodic and interesting to play alone (you can also adapt most violin parts) to portability, and the market for flutists is not nearly so glutted as that for violins. However it is an indisputable fact that flutes are barely heard. Even if sensitive ears can tell that something is off, it will be difficult for them to blame it on the flutes.

Once in marching band (which is admittedly much less precise than orchestra) a fellow flutist and I decided to test the hypothesis that flutes are sometimes ignored. We played "happy birthday" during an entire fight song and no one even told us we were off key. After that I quit band.

So you can understand my bias when I say that besides tuba, you might also want to look into percussion.

Ram,

Several people I know took up singing and joined a choir. There are many of those around. It is both quite easy and the minimal requirement are really minimal, but also there is a really nice sensation from having your instrument being your own body, something you don't get from playing the Piano, or other instruments. Some even became really good at it, and started to be semi-professional in their time off.

Of course you might really not like it, and then I could suggest a wind instrument which, sometimes, is good for your health as it develops good breathing, but then it is not that easy, and your neighbors won't appreciate it.

And then there is always the good old triangle - you can't miss with that.

Hi Ram,

I agree with Virginia  that singing in a choir is the best second instrument to take on. It’s very good for your posture, it makes you aware and connected to your body and I think it’s very healthy to let yourself scream out your daily aggressions in a cultivated way (I believe that everyone should take on singing lessons anyway). The problem is that some people and even professional musicians simply cannot sing in tune, don’t ask me why. So if we are talking about any other instrument that would be useful in an orchestra, in which you could have a modest part (especially as a beginner), feel you are making music with everybody without attracting too much attention or having a too important and difficult part, I would say to go for the Contrabass. The contrabass is the base of every orchestra. It’s so important that there are always at least a few of them playing the same part, which makes you much less exposed to being recognized in case you miss something. It has no solos at all like the wind instruments or the other string instruments (unless they just double a cello solo, and you can just skip this part and no one would notice). Also, it’s a huge instrument that is usually left in the rehearsal place (which is a nice space economy in your house), and maybe as a beginner you could put some stickers on where the notes are so that you could find them easily, then you just need to work on how to produce a beautiful Bass sound. It is funny to see how little attention this big instrument attracts in the orchestra, and actually Susskind has written a book on this subject called “the contrabass player”.