I am starting to go through the exercises in first position on Rabbath's first book and his sound in the accompanying CD is so beautiful and clean. it has no grainniness for lack of a better word, like he is playing harmonics in each note. I know he does advocate for little to no rosin. is that and arm weight what makes the difference? does he angle the bow to reduce the amount of hair or uses full hair?
There are many, many factors contributing to the tone you're describing. Technique, equipment, recording technology, lots of practice, and no small amount of talent.
On the equipment side, it's worth remembering that he's using a very fine, old bass strung up with custom-made strings and some of the best bows in the world.
He uses more rosin than you might think, but less than your average orchestra player. I believe he still uses Pops.
Fred Emens said:
The position of the bow relative to the bridge is very important and each note has its own sweet spot for production of the best tone.
This is one of the defining characteristics of FR's playing. The concept is called
son premier, or "primary sound." The idea is that a bowed string's best sound comes when it is vibrating as openly as possible. According to Rabbath, this is best achieved by placing the bow near the 7th harmonic partial closest to the bridge for the given pitch. For example, an open G string would be played with the bow placed on or near the high F-natural harmonic at the end of the fingerboard. One whole step higher, the A in first position, would require the bow to move one whole step closer to the bridge (meaning the G, which would be the 7th harmonic partial for the "A" string).
That might sound like gibberish, but it totally works. The technique does require you to use a slightly faster bow than you are perhaps used to, and a lighter touch so as to not grind out. Put very simply, Rabbath plays closer to "sul tasto" than most other people.