constructEnv = function(arg){
	return { //default envelope, if one is not specified on play
		attack   : lodash__WEBPACK_IMPORTED_MODULE_3___default.a.get(arg, 'env.attack', 0),    // time in seconds from onset to peak volume
		decay    : lodash__WEBPACK_IMPORTED_MODULE_3___default.a.get(arg, 'env.decay', 0),    // time in seconds from peak volume to sustain volume
		sustain  : lodash__WEBPACK_IMPORTED_MODULE_3___default.a.get(arg, 'env.sustain', 1),    // sustain volume level, as a percentage of the max
		hold     : lodash__WEBPACK_IMPORTED_MODULE_3___default.a.get(arg, 'env.hold', 3.14159),    // time in seconds to maintain sustain volume
		release  : lodash__WEBPACK_IMPORTED_MODULE_3___default.a.get(arg, 'env.release', 0),    // time in seconds from release to zero volume
	};
}
Set up the default ADSR envelope. *