Abstract: Methods and apparatus for automatically mixing a plurality of audio channels by adjusting respective gains of the audio channels using a control signal based on an aggregate of input levels of respective audio signals of the audio channels; and reducing the gain of a given one of the audio channels when an input level of the audio signal of that audio channel exceeds a threshold, irrespective of whether the control signal would permit the gain to rise higher.

Abstract: Methods and apparatus for adjusting a tonal quality of an audio signal include functional elements and/or steps, comprising producing a first intermediate signal containing a band of frequencies at a lower mid-range of the audio signal; producing a second intermediate signal containing a band of frequencies at an upper mid-range of the audio signal; combining the first intermediate signal, the second intermediate signal and the audio signal to produce a tonally adjusted version of the audio signal; and adjusting respective gains of the first and second intermediate signals to affect the tonal quality of the audio signal without substantially altering the tonal quality of the audio signal at frequencies between the lower mid-range and the upper mid-range.

Abstract: Methods and apparatus may provide for one or more of: receiving an input signal containing frequencies from among a first range; filtering the input signal to produce a first intermediate signal containing frequencies from among a second range; producing a sub-harmonic signal from the first intermediate signal containing frequencies from among a third range, the third range of frequencies being about one octave below the second range of frequencies; canceling energy at at least some frequencies from among a fourth range of frequencies from a left channel signal of the input signal to produce at least a portion of a left channel output signal; and canceling energy at at least some frequencies from among a fifth range of frequencies from a right channel signal of the input signal to produce at least a portion of a right channel output signal.

Abstract: Methods and apparatus are disclosed that achieve sub-harmonic signal processing, stereo-width expansion, sub-woofer signal processing, and tube distortion emulation to achieve various desirable acoustic effects when used to modify an input signal containing, for example, music content.