Performing Tetras, on the other hand, feels more like like an extreme sport [in contrast to ST/4]. It could be that some of the more difficult cerebral challenges of playing the work have thoroughly entered muscle memory for me after dozens of performances, but the energy required from the moment our quartet started learning the piece is decidedly very physical. However, I still experience some level of conflict between the physicality of action and the kind of mental control that must be established. There is a kind of conscience or nagging voice-of-reason that tells me I could be producing the same sonic result if my technique were more focused, and my energies more direct, in other words if my body was much more relaxed and everything was functioning like some sort of well-oiled machine. However, in a handful of performances where I have attempted to do just this the result was somehow deeply unsatisfying. To give a successful performance of Tetras I have become convinced that I must give literally everything I have, so that by the end of the intensely loud and explosive tremolo glissandi concluding the piece, when the dynamic drops drastically and the tempo asymptotically approaches complete stillness, the energy dissipates in a way that is not entirely controlled but dissolves into space precisely because nothing is left. That is not to say that energy is not metered out and paced, because it is crucial that the absolute maximum level of output is reached only a minute or so before the end of the piece. However, there are not very many places to fuel up along the way either, if one's tank is not to end up prematurely out of gas.