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How Does the Shazam App Work in Identifying Music

How Does the Shazam App Work in Identifying Music

Shazam can conjure up a lot of information about a mystery song such as its name, the name of its artist, its download link etc. just by listening to it through your smart-phone's speaker. But how does it do it? Is it really magic? In this Techspirited article, we answer those questions and give a brief overview of how the music identification software Shazam works its magic.
Satyajeet Vispute
Did You Know?
The Shazam app was listed among Techland's 50 Best Android Applications for 2013. At present, the company claims to have over 500 million users worldwide
One fine morning, you go to your favorite coffee shop. As you sit there sipping your brew, you find your feet tapping along to the groovy beats of the song that's playing over the speakers. You decide that you want that song. Unfortunately however, you neither know the name of the artist nor that of the song. So what do you do? You ask the resident wizard on your smartphone for help. Abracadabra, hocuspocus, bibedi-babedi-boo, and within seconds, he brings you all the details of that mystery song.

Amazing isn't he? Indeed! And with a name like Shazam, there is no wonder that he can perform miracles. This all-powerful software application is one of the wonders of modern-times, which is all set to redefine our musical experience. In the following lines, we shall learn more about it, and also try to find out the secret behind its magic.
What is Shazam?
Shazam is a media engagement company which is headquartered in London. It provides a music recognition service which is especially designed for smartphones users. The company was originally founded in the year 1999 by Philip Inghelbrecht, Chris Barton, Avery Wang, and Dhiraj Mukherjee, with a vision to connect people across the world to the music that they love.

In 2002, Shazam first started off as a telephonic service, where the user could dial '2580' to get music recognized. A few years later, with the advent of smartphones, the company evolved to a totally Internet based service. In July 2008, Shazam became one of the first apps to be featured on the revamped Apple applications store. In September of the same year, it was also made available for Android users.

Today, Shazam offers two applications - a free trial program named simply as Shazam, and a paid one called Shazam Encore. Both these can operate over several operating platforms, including Apple iPhones, Android devices, BlackBerry devices, Nokia smartphones, etc.
What Does Shazam Do?
Shazam provides music recognition services to its customers. Initially, the user was required to dial '2580 and hold the phone's mic against the source of music. After 30 seconds, the phone used to automatically hang-up, and the user would receive a text message containing the song's details.

Nowadays, Shazam comes in the form of an app on smartphones. Once this app is downloaded and installed, it can recognize almost any music that you ask it to. This app is the same on most smartphones. The user is only required to launch it on their device, and it will provide a list of all the details of the song on the phone's screen.

Included in this list are the names of the artist, album, title, genre, music label, lyrics, and a thumbnail image of the song/album artwork. It even sends you links to download the song on iTunes or the Amazon MP3 store. If a video is available, it sends you a YouTube link as well.
How to Use the App
In the company's lingo, the process where you use Shazam to identify a song is called Shazaming. The following are the steps involved in Shazaming.

1) Launch the Shazam app on your device.

2) Hold it towards the source of the audio to begin Shazaming it.

3) In a matter of seconds, the sample audio will be Shazamed, that is, identified, and you will get all the details of the song.
How Does Shazam Work?
Shazaming truly seems like magic. However, there is solid science and technology behind it. The following is a look at the inner workings of the magical feat that Shazam performs.

A magician prepares for his act by readying the tools and instruments that he will be using for his performance. The main instrument that Shazam uses for music identification is its comprehensive music database, which is updated and kept ready at all times. This is the most important part of the entire song identification process.

Shazam's signal processing algorithm performs a digital fingerprinting on each and every song that is fed into it. It creates a 3D-graphical plot of the song, known as the spectrogram, based on three different parameters within it. In the spectrogram, time is plotted along the X axis, while frequency is plotted along the Y axis. The third parameter, intensity, is plotted along the Z axis. Thus, each point on this graph is the plot of the intensity of a particular frequency at a particular instant of time. The following is a simplified version of this graph, showing only the X and Y axis.
shazam song frequencies
All songs are made up of several frequencies. Shazam tracks these frequencies, and once a frequency hits a high point, known as 'peak frequency', Shazam makes a note of it along with the particular instant of time from the start that it appears in the song. This information is then compiled in the form of a hash table, for which the frequency is used as the key and stored in the database. This is represented by the following table.

Frequency in Hz. Time in Seconds
752.44 1.501
1942.12 1.793
632.82 2.012
........... ............

Thus, effectively, each song is fingerprinted according to its peak frequencies, and is stored in Shazam's database.

After fingerprinting is done, Shazam is all set to perform the magic of track identification. The user is required to 'tag' a song that he/she wants identified. Tagging is the process where a 10-second sample of the song is recorded by the application via the phone's mic. This sample is then fingerprinted, based on the above mentioned algorithm, and the frequency-intensity-time values so generated are compared one by one with those of the numerous songs that are stored in the database. This continues until a match is found.

If matching occurs, all the available details of the song are sent forth to the user's device. Otherwise, an error message is generated.
The Power of Shazam
Shazam currently has a database that is over 12 billion songs strong. These include an extensive coverage of music from different genres and from nearly 100 different countries. Hence, it is practically good for identifying almost any song that you hear over the radio or on TV, provided that the song is fingerprinted in its database.
Limitations of Shazam
The all-powerful Shazam does have a few limitations. One important limitation is that it works only on pre-recorded music, and only if it is stored in Shazam's database. Shazam does not work on live music playing at a concert. However, do note that it can still work on pre-recorded live music.

Apart from that, Shazam's database currently features only a limited number of songs from specialized genres such as Jazz and Classical. So don't expect any miracles there. Also, in an environment that has a lot of background noises and disturbances, Shazam might not be able to work its magic.

Lastly, things like humming a tune or drumming on the table are not recognized by the app.
Thus, Shazam the powerful, is a very useful application that truly works wonders in helping you identify and get in touch with the music that you love. It is true that it does have a few limitations, but with continuous research and development in the field of digital signal processing, the day isn't far when this program becomes truly great.