Music Transcription

A method of generating score data from an audio signal, the method comprising:

• identifying a change in frequency information from the audio signal that exceeds a first threshold value;
• identifying a change in amplitude information from the audio signal that exceeds a second threshold value;
• and
• generating a note onset event, each note onset event representing a time location in the audio signal of at least one of an identified change in the frequency information that exceeds the first threshold value or an identified change in the amplitude information that exceeds the second threshold value.

A method of generating tempo data from an audio signal, the method comprising:

• determining a set of reference tempos;
• determining a set of reference note durations, each reference note duration representing a length of time that a predetermined note type lasts at each reference tempo;
• determining a tempo extraction window, representing a contiguous portion of the audio signal extending from a first time location to a second time location;
• generating a set of note onset events by locating the note onset events occurring within the contiguous portion of the audio signal;
• generating a note spacing for each note onset event, each note spacing representing the time interval between the note onset event and the next-subsequent note onset event in the set of note onset events;
• generating a set of error values, each error value being associated with an associated reference tempo, wherein generating the set of error values comprises:
• dividing each note spacing by each of the set of reference note durations;
• rounding each result of the dividing step to a nearest multiple of the reference note duration used in the dividing step;
• and
• evaluating the absolute value of the difference between each result of the rounding step and each result of the dividing step;
• identifying a minimum error value of the set of error values;
• and
• determining an extracted tempo associated with the tempo extraction window, wherein the extracted tempo is the associated reference tempo associated with the minimum error value.

A method of generating key data from an audio signal, the method comprising:

• determining a set of cost functions, each cost function being associated with a key and representing a fit of each of a set of predetermined frequencies to the associated key;
• determining a key extraction window, representing a contiguous portion of the audio signal extending from a first time location to a second time location;
• generating a set of note onset events by locating the note onset events occurring within the contiguous portion of the audio signal;
• determining a note frequency for each of the set of note onset events;
• generating a set of key error values based on evaluating the note frequencies against each of the set of cost functions;
• and
• determining a received key, wherein the received key is the key associated with the cost function that generated the lowest key error value.

A method of generating track data from an audio signal, the method comprising:

• generating a set of note onset events, each note onset event being characterized by at least one set of note characteristics, the set of note characteristics comprising a note frequency and a note timbre;
• identifying a plurality of audio tracks present in the audio signal, each audio track being characterized by a set of track characteristics, the set of track characteristics comprising at least one of a pitch map or a timbre map;
• and
• assigning a presumed track for each set of note characteristics for each note onset event, the presumed track being the audio track characterized by the set of track characteristics that most closely matches the set of note characteristics.

A computer-readable storage medium having a computer-readable program embodied therein for directing operation of a score data generation system including an audio receiver configured to receive an audio signal, a signal processor configured to process the audio signal, and a note processor configured to generate note data from the processed audio signal, the computer-readable program including instructions for generating score data from the processed audio signal and the note data in accordance with the following:

• identifying a change in frequency information from the audio signal that exceeds a first threshold value;
• identifying a change in amplitude information from the audio signal that exceeds a second threshold value;
• and
• generating a note onset event, each note onset event representing a time location in the audio signal of at least one of an identified change in the frequency information that exceeds the first threshold value or an identified change in the amplitude information that exceeds the second threshold value.