Musipedia
Encyclopedia
Musipedia is a search engine for identifying pieces of music. This can be done by whistling a theme, playing it on a virtual piano keyboard, tapping the rhythm
on the computer keyboard, or entering the Parsons code
. Anybody can modify the collection of melodies and enter MIDI files, bitmaps with sheet music (possibly generated by the Musipedia server after entering LilyPond or abc source code), lyrics or some text about the piece, or the melodic contours as Parsons Code.
alone.
The melodic contour search uses an editing distance. Because of this, the search engine finds not only entries with exactly the contour that is entered as a query, but also the most similar ones among the contours that are not identical. Similarity is measured by determining the editing steps (inserting, deleting, or replacing a character) that are needed for converting the query contour into that of the search result. Since only the melodic contour is relevant, one can find melodies even if the key
, rhythm
, or the exact intervals
are unknown.
The pitch and onset time-based search takes more properties of the melody into account. This search method, which is used by default, is still transposition-invariant and tempo-invariant, but it takes rhythm and intervals into account. The melody can be entered in various ways, for example by clicking on a virtual keyboard
on the screen. The search engine then segments the query, converts each segment into a set of points in the two-dimensional space of onset time and pitch, and, by using the Earth Mover's Distance
, compares each point set to pre-computed point sets representing segments of melodies from the database. As with the contour search, little alterations of the query will lead to correspondingly small changes in the results, which makes the search method somewhat error-tolerant.
The "query by tapping" method that only takes the rhythm into account uses the same algorithm as the pitch and onset time method, but assumes all pitches to be the same. As a result, the algorithm can be used for tapped queries that only contain onset times.
Both search algorithms are made faster with indices that are based on vantage objects. Instead of calculating the distance between the query and every single database entry, Musipedia just calculates the distance between the query and each of a few vantage objects. For every vantage object, the distance to each database entry is known. Since the triangle inequality
holds for both the editing distance for contours and the variant of the Earth Mover's Distance used by Musipedia, the search algorithm needs, in a second step, to take a closer look at only those database entries whose distances to the vantage objects are similar to the distances between the query and the vantage objects.
. The latter can identify short snippets of audio (a few seconds taken from a recording), even if it is transmitted over a phone connection. Shazam uses Audio Fingerprinting
for that, a technique that makes it possible to identify recordings. Musipedia, on the other hand, can identify pieces of music that contain a given melody. Shazam finds exactly the recording that contains a given snippet, but no other recordings of the same piece.
Since 2006, the Musipedia search engine can also be used for searching the world wide web
for MIDI files. Musipedia locates the MIDI files that go into its search index by using the Alexa Web Search service, which has been available since December 2005 (as described by Planet.nl and the Wall Street Journal).
Rhythm
Rhythm may be generally defined as a "movement marked by the regulated succession of strong and weak elements, or of opposite or different conditions." This general meaning of regular recurrence or pattern in time may be applied to a wide variety of cyclical natural phenomena having a periodicity or...
on the computer keyboard, or entering the Parsons code
Parsons code
The Parsons code, formally named the Parsons Code for Melodic Contours, is a simple notation used to identify a piece of music through melodic motion—the motion of the pitch up and down. Denys Parsons developed this system for his 1975 book, The Directory of Tunes and Musical Themes...
. Anybody can modify the collection of melodies and enter MIDI files, bitmaps with sheet music (possibly generated by the Musipedia server after entering LilyPond or abc source code), lyrics or some text about the piece, or the melodic contours as Parsons Code.
Search principles
Musipedia offers three ways of searching: Based on the melodic contour, based on pitches and onset times, or based on the rhythmRhythm
Rhythm may be generally defined as a "movement marked by the regulated succession of strong and weak elements, or of opposite or different conditions." This general meaning of regular recurrence or pattern in time may be applied to a wide variety of cyclical natural phenomena having a periodicity or...
alone.
The melodic contour search uses an editing distance. Because of this, the search engine finds not only entries with exactly the contour that is entered as a query, but also the most similar ones among the contours that are not identical. Similarity is measured by determining the editing steps (inserting, deleting, or replacing a character) that are needed for converting the query contour into that of the search result. Since only the melodic contour is relevant, one can find melodies even if the key
Key (music)
In music theory, the term key is used in many different and sometimes contradictory ways. A common use is to speak of music as being "in" a specific key, such as in the key of C major or in the key of F-sharp. Sometimes the terms "major" or "minor" are appended, as in the key of A minor or in the...
, rhythm
Rhythm
Rhythm may be generally defined as a "movement marked by the regulated succession of strong and weak elements, or of opposite or different conditions." This general meaning of regular recurrence or pattern in time may be applied to a wide variety of cyclical natural phenomena having a periodicity or...
, or the exact intervals
Interval (music)
In music theory, an interval is a combination of two notes, or the ratio between their frequencies. Two-note combinations are also called dyads...
are unknown.
The pitch and onset time-based search takes more properties of the melody into account. This search method, which is used by default, is still transposition-invariant and tempo-invariant, but it takes rhythm and intervals into account. The melody can be entered in various ways, for example by clicking on a virtual keyboard
Virtual keyboard
A virtual keyboard is a software component that allows a user to enter characters. A virtual keyboard can usually be operated with multiple input devices, which may include a touchscreen, an actual keyboard and a computer mouse.- Types :...
on the screen. The search engine then segments the query, converts each segment into a set of points in the two-dimensional space of onset time and pitch, and, by using the Earth Mover's Distance
Earth Mover's Distance
In computer science, the earth mover's distance is a measure of the distance between two probability distributions over a region D. In mathematics, this is known as the Wasserstein metric...
, compares each point set to pre-computed point sets representing segments of melodies from the database. As with the contour search, little alterations of the query will lead to correspondingly small changes in the results, which makes the search method somewhat error-tolerant.
The "query by tapping" method that only takes the rhythm into account uses the same algorithm as the pitch and onset time method, but assumes all pitches to be the same. As a result, the algorithm can be used for tapped queries that only contain onset times.
Both search algorithms are made faster with indices that are based on vantage objects. Instead of calculating the distance between the query and every single database entry, Musipedia just calculates the distance between the query and each of a few vantage objects. For every vantage object, the distance to each database entry is known. Since the triangle inequality
Triangle inequality
In mathematics, the triangle inequality states that for any triangle, the sum of the lengths of any two sides must be greater than or equal to the length of the remaining side ....
holds for both the editing distance for contours and the variant of the Earth Mover's Distance used by Musipedia, the search algorithm needs, in a second step, to take a closer look at only those database entries whose distances to the vantage objects are similar to the distances between the query and the vantage objects.
Differences between Musipedia and audio search engines
Musipedia's search engine works differently from that of search engines such as ShazamShazam Entertainment
Shazam Entertainment is a company that provides a commercial music identification service through acoustic fingerprinting. A user calls a telephone number provided by Shazam while the music to be identified is playing...
. The latter can identify short snippets of audio (a few seconds taken from a recording), even if it is transmitted over a phone connection. Shazam uses Audio Fingerprinting
Acoustic fingerprint
An acoustic fingerprint is a condensed digital summary, deterministically generated from an audio signal, that can be used to identify an audio sample or quickly locate similar items in an audio database....
for that, a technique that makes it possible to identify recordings. Musipedia, on the other hand, can identify pieces of music that contain a given melody. Shazam finds exactly the recording that contains a given snippet, but no other recordings of the same piece.
History
Musipedia was started by Rainer Typke in 1997 and has been developed by him since then. Before the Wikipedia-like collaboration features were added (editing and deleting existing entries has been possible only since 2004), he called the music search engine "Melodyhound".Since 2006, the Musipedia search engine can also be used for searching the world wide web
World Wide Web
The World Wide Web is a system of interlinked hypertext documents accessed via the Internet...
for MIDI files. Musipedia locates the MIDI files that go into its search index by using the Alexa Web Search service, which has been available since December 2005 (as described by Planet.nl and the Wall Street Journal).