detection algorithms is to search the spectrogram for the occurrence of such comb patterns (a composite of harmonics) caused by individual notes. Once the pattern of a note's particular comb shape of harmonics is detected, the note's pitch can be measured by the vertical position of the comb pattern upon the spectrogram. There are basically two different types of music which create very different demands for a pitch detection algorithm: monophonic music and polyphonic music. Monophonic music is a passage with only one instrument playing one note at a time, while polyphonic music can have multiple instruments and vocals playing at once. Pitch detection upon a monophonic recording was a relatively simple task, and its technology enabled the invention of guitar tuners in the 1970s. However, pitch detection upon polyphonic music becomes a much more difficult task because the image of its spectrogram now appears as a vague cloud due to a multitude of overlapping comb patterns, caused by each note's multiple harmonics. Another method of pitch detection was invented by Martin Piszczalski in conjunction with Bernard Galler in the 1970s and has since been widely followed. It targets monophonic music. Central to this method is how pitch is determined by the human ear. The process attempts to roughly mimic the biology of the human inner ear by finding only but a few of the loudest harmonics at a given instant. That small set of found harmonics are in turn compared against all the possible resultant pitches' harmonic-sets, to hypothesize what the most probable pitch could be given that particular set of harmonics. To date, the complete note detection of polyphonic recordings remains a mystery to audio engineers, although they continue to make progress by inventing algorithms which can partially detect some of the notes of a polyphonic recording, such as a melody or bass line. Beat detection Beat tracking is the determination of a repeating time interval between perceived pulses in music. Beat can also be described as 'foot tapping' or 'hand clapping' in time with the music. The beat is often a predictable basic unit in time for the musical piece, and may only vary slightly during the performance. Songs are frequently measured for their Beats Per Minute (BPM) in determining the tempo of the music, whether it be fast or slow. Since notes frequently begin on a beat, or a simple subdivision of the beat's time interval,