This technique is used by composers to create a muted and haunting tone, it also gives a great visual component to a performance. George Crumb uses this technique in Black Angels where he tells the performers to hold the violins between their knees to give the appearance of playing a viol. The other version that can be used is in the normal playing position where the performer has to reach their right arm round. I found playing the second a lot more difficult, surprisingly, than the ‘viol’ version. I feel that this is because whilst you are concentrating on bowing in a position that is completely different the performer also has to consider the fact that the fingers are going in reverse. Say you go from a D to an E in third position on the G string, the pitch gets higher as the vibrating section of the string is decreasing in length whereas if you play behind the fingerboard then if you play the same notes it comes out as an A to a G on the E string.
Composers should also take note that the only strings that this technique is suited for is the G and the E string on the violin. It should also be noted that there will be a rosin build up on the strings where it would be usual for the fingers to go meaning that there should be adequate time for the performers to wipe away any rosin. If it is a substantially long passage then a second violin may be needed.
For performing this technique in the ‘viol’ position I found that playing about 1cm away from the nut gave the optimum sound. As a performer you also have to be wary of clipping the D and A strings, as they will resonate more it is very noticeable. Playing this technique in the normal position I found that having a very strait bow was very useful so that other strings were not touched accidentally. With both of the positions I found that using quite a fair amount of bow pressure helped to create a pleasant tone. It should also be noted that fingers have to be lifted after each note so that the next one can be heard.
A written instruction above the music is usual for this technique