Leland Stanford Junior University

David A Jaffe

Julius O Smith

Scott A Van Duyne

Timothy S Stilson

Gregory P Scandalis

A sampled data, delay line structure that includes a sampled data delay line, two readers for reading data at corresponding positions of the delay line, controller that controls when the read position of each reader is updated for a new note of a different pitch, and a crossfader that crossfades between the outputs of the two readers to produce a legato transition between the two discrete notes associated with the two readers. The controller receives a control signal indicating a sequence of note events to be implemented by the delay line structure. When a new note on event occurs while a previous note is still playing, a legato crossfade sequence is performed. In particular, the delay line reader not used by the previous note is set to a delay position associated with the new note, and the crossfader is enabled. The crossfader gradually transitions its output from that of the reader used for the previous note to the output of the reader used from the new note. Each reader may include an interpolation filter, such as an allpass filter, so that the delay line length associated with each note can be a non-integer value. The crossfade ramp used by the crossfader is preferably an 's-shaped' non-linear function.

Digital signal processing system and method for generating musical

A sampled data, non-integer delay line interpolation structure includes a sampled data delay line, two allpass filters, each having an associated read pointer for reading data at a corresponding integer position of the delay line, an alternating crossfader that alternatingly crossfades between the outputs of the two allpass filters, plus a controller that controls when the read position of each allpass filter is updated and also controls when the filter coefficient of each allpass filter is updated. A specified delay length value is sampled by the controller each time the crossfade orientation of the alternating crossfader is changed, and from that value the controller generates a new read pointer and filter coefficient for allpass filter to which the structure will next crossfade. The new read pointer is an integer that corresponds to an integer portion of the specified delay length, and the filter coefficient corresponds to a fractional portion of the specified delay length. After updating the read pointer and filter coefficient of one allpass filter, the alternating crossfader outputs the signal generated by the other allpass filter for a first number of sample periods until the updated filter 'warms up.' Then the alternating crossfader crossfades to the signal generated by the updated allpass filter over a second number of sample periods. At the end of the crossfade operation the specified delay line length is sampled again, the reader position and filter coefficient of the other allpass filter is updated, and then the crossfade operation repeats.

Growing community of inventors

Berkeley, CA, United States of America

David A Jaffe