Because the low-bit (192 kilobits per second) conversion encoder / decoder system (44.1 KHz or 48 KHz sampling rate) for high quality music applications uses a short time-domain sample block (128 sample blocks), the system signal transmission delay is Is short enough for real-time auditory feedback. Carefully designed pairs of analysis / synthesis windows are used to achieve sufficient conversion frequency selectivity despite the use of short sample blocks. The synthesis window of the decoder has the property of producing a complex response where the product of its response and the response of the encoders analysis window is summed as 1 for two adjacent superimposed sample blocks. Adjacent time domain signal sample blocks are superimposed and added to remove the effects of analysis and synthesis windows. Techniques for deriving appropriate analysis / synthesis window pairs are provided. In an encoder, a discrete transform, or alternatively a discrete Fourier transform, with a function by alternating application of modified DCT and modified DST by time-domain aliasing cancellation techniques is used to generate the frequency domain transform coefficients. The transform coefficients are nonuniformly quantized by assigning a fixed number of bits and a variable number of bits adaptively determined based on psychoacoustic interception. Techniques for assigning fixed bits and adaptive bits are described. The transmission of the measurement beams for adaptively allocated bits is not necessary. Error codes and protected data can be distributed through the formatted frame output from the encoder to reduce sensitivity to noise bursts.