While virtual reality and 3D interaction provide new possibilities for musical applications, the existing immersive virtual instruments are limited to single process instruments or musical navigation tools. In this paper we present the 3D reactive widgets. These graphical elements enable simultaneous control and visualization of musical processes in 3D immersive environments. They also rely on the live-looping technique, allowing to build complex musical sequences. We describe the interaction techniques that we have designed and implemented to manipulate these widgets, including a virtual ray and tunnels. After having expressed the lack of expressivity and efficiency of the existing input devices for sound production gestures, we finally set the requirements for an appropriate device for musical interaction in 3D immersive environments.