I am a trained Indian Carnatic style violin player. Can I play Western songs on a violin with carnatic fingering techniques or do I need to re-learn everything to adopt to the Western style?
If you already play a very difficult music style, I think to pass to western music will be easier for you. The only difficulty will be to adapt to this other system with different "rules".
Watch this video,
If You Can Play Carnatic Music, You Can Play Anything | Akkarai Subhalakshmi | Music of India:
You can play western songs with the fingering techniques of carnatic violin if you are skilled enough to give up the traditional basic finger positions to follow. If you can play any notes with any finger spontaneously this is possible either to play carnatic music in western violin or western music in carnatic violin. The challenge is when it comes to the continuity of notes from third string to the second string. In carnatic way of tuning, the strings are Sa, Pa, Sa, Pa in the order of strings 4,3,2 and 1. Same swaras in the next octave is arranged for strings 4 and 3 in 2 and 1 respectively. But in Western way of tuning, it is G, D, A, E. This difference exist because the fourth note (third finger) in the third string is same as the first note (without finger) in the second string for Carnatic violin. But it is the fifth note (fourth finger) in the third string for Western violin that is tuned same as the first note (without finger) in the second string. These become confusing for a beginner if to try both together when you start learning. Once expertise in either of the style first and then learning the other style afterwards will provide some stability. However, once you master the basic finger chart and go beyond to attain a freedom of fingers to play any note with any finger, it will be easy.
Edit: One easy workaround is to use 'D' string (third) as base swara for 'Sa'. In this way we are able to play 'Sa' on the third string of western violin and 'Pa' on the second string. By doing this, we can have one complete octave (and another half octave if the higher second positions played in this new second string 'pa' up until the higher 'pa'). This leave us with the option of only two strings to play Carnatic music on western violin. However, we can have one more string if we slightly adjust the fourth string as the lower 'pa'. Here the fourth string has to work as the third string of Carnatic. Now it adds half octave below too. Usually most of the songs require this much range of pitch only (most of the humans sing within these). The flute is having this much range only. But remember that this is just a workaround. Even if we get the 'pitch' equal, may be we have to compromise the 'tone' when it is significant for some particular pieces/songs (because we are using a thicker strings for 'Sa' and 'Pa'). Although it is okay for just simple play if we ignore tone, etc. If it is 5 string violin, we can dedicate separate strings for the G of western and Pa of Carnatic rather than changing the pitch each time. Then it would be like G, Pa, D, A, E.