For me it's been a case of having and instrument which naturally rises to the fore depending on what I am trying to achieve in life. When I was singing for festivals the vocal practice came through, then I was doing orchestral stuff and it was all viola for a while. In my A-levels I was doing viola for principal and recorder for second study, but when I started at college I was below the required minimum standard on keyboard so I had to take second study piano lessons, so recorder sort of fell back. Then I joined the recorder group and they let me play their awesome beast the F contrabass, so I ended up getting into trouble for the standard of my two main studies! So back to viola for a bit, meanwhile choir became compulsory too. After that music degree gave me a nervous breakdown
I calmed down to doing what I wanted to do, the viola sat on the side a wee bit, it came out for fun but not for recitals.
There followed the army band where they wanted wind instruments, so I had to get flute back up to standard and studied for my TEQ exam (forces in-house examinations, grades equivalent to 6, 7 and 8 or thereabouts). Then they threw a piccolo at me for outdoor gigs, then told me there was no flute in the jazz band, you have to learn the alto sax!
Then they wanted me on keyboard, then when I truly ran out of other instruments I had to join the percussion section - all depended if we were marching or what.
After coming out of the army band I wanted to go back to teaching, so the viola came back to the first study, the flute went for a long lie down (it's in shocking condition anyway, when I was in the army band I used their flute). But of course people want violin lessons, not so much viola lessons, so I had to start looking towards taking a violin exam.
Just now I am in the SRP so the recorder is coming back to the top of the pile again, so I suppose I would say my first study is viola and second is recorder, the rest I get to if I get to it, and I'll polish it up if someone needs me for a fiddle band or a flute choir. You wouldn't imagine I'd need any more instruments, but I'm off to look at a clarasch in the next few weeks.
And they have a Moeck baroque oboe in stock, they'd stopped making them and I WANT IT SO MUCH! But I cannot play the oboe at all, I have no real need to own one, I'm sure it's the recorder player in me that looks at the beauty of the instrument and needs to make it sing, but I somewhat doubt I am the right woman for the job!
Not sung in a serious way for years, but I walked past a copy of Carols for Choirs in the music shop the other day and nearly went weak at the knees.
So I guess you could say I never do manage to keep it all "ticking over", but nor is my first study always the same instrument. And you do have to be ready for multiple nervous breakdowns, I think. How I did 8 choirs, 5 orchestras, put on a nightly performing opera tour and sat my A levels and grade 8 at the same time will never be clear, I counted the hours a week I spent on music and I'm sure it came to more than the total number of weekly hours.