That’s easy—dance.
It’s one of the mysteries of playing contemporary music for so many classical string players: how can I get some swing or groove into my playing when I’m playing non-classical music? I always sound so classical!
Well, there are a few things that may be making you sound classical—your vibrato is a big one.
But the solution to the groove mystery is very simple, although some people may not be inclined to do it. Just move to the music. Dance a little.
Play a recording of a tune you like—something with a definite groove that people might dance to.
Start by tapping your foot. Then nod your head with your foot taps.
Then add a little bit knee bends on each tap so you are bouncing up and down a bit. Then snap your fingers on the 2nd and 4th beats.
Then lean from side to side with each tap so that you are shifting your weight on your feet.
Make sure you are locking to the groove of the music while you are doing this!
Let your body respond to the music this way for 5 or 10 minutes. This is not about choreography or anything like that, but let’s call this “dancing” to the music.
Then make sure whatever you are playing on your instrument is easy enough for you to play that you can do it while you are “dancing”.
Then, rather than fighting what that does to your bow arm, let the movement of your body influence your bow strokes in terms of accents, etc.
That’s how you get the groove into your playing.