Let's say I have a tune in my mind, one I have invented and so there isn't any sheet music for it still. I would like to play it on the violin. What strategy can I use to find out what strings to use and where to press them?
For the guitar I just play all notes from the lowest to the highest until I find the one nearest to the first I can whistle (since human whistle is quite high in pitch, I may decide to transpose this note one octave sometimes, to not go past the highest available pitch on the guitar) That fixes my first note. Then I play a second note starting from the first and going either up or down until I find what matches the tune second note as I can whistle and so on. Since there are frets, I have a discrete set of pitches (ignore bending effects, which I only add later as embellishments).
But on a fiddle, how to do that? Is it right if I se vibrato to correct the pitch until it matches the note I whistle? How am I going to remember right-hands positions without frets? Just muscle memory?
How do you composers find out notes for a music you have in your head on the violin? I am especially interested to play a music I am thinking that has the timbre of the violin.