Dave J Hogan/Getty Images (Ed Sheeran); Rick Kern/WireImage (Grace VanderWaal); Hutton Supancic/Getty Images for SXSW (Khalid);  illustration by Vanessa Irena for Scholastic

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Playlist Programmer

Oscar Celma predicts which tunes you’ll love

February 2020
By Jeanette Ferrara

How do you decide what music to listen to? If you use a music-streaming service such as Pandora, you use its app to discover new tunes. Listeners can type in an artist they like—say, BTS or Taylor Swift. Then Pandora uses the information to create custom playlists. Each is filled with similar-sounding songs by different artists.

Oscar Celma is a computer scientist and the head of research at Pandora. He helped design the app. His team at Pandora studies data from the app’s users. The team uses the information to predict listeners’ musical preferences and recommend new music.

How do you decide what music to listen to? If you use Pandora, you use its app to discover new tunes. Pandora is a music-streaming service. Listeners can type in an artist they like. Then Pandora creates custom playlists. Each is filled with similar-sounding songs by different artists.

Oscar Celma is a computer scientist. He's the head of research at Pandora. He helped design the app. His team at Pandora studies data from the app’s users. They use the information to recommend new music.

Music Matters

Josh Miller/CNET

Oscar Celma

Celma considers music more than his work—it’s his passion. He started playing the guitar at age 12. Around the same time, he developed a love of computer programming. Programmers write instructions, called code, that tell computers what to do. Celma studied computer science in college. After he graduated, he combined both his interests in his work. 

“I built algorithms—sets of rules that a computer uses to solve a problem—for recommending music,” he explains. “I tried to improve the music my program suggested by including songs that weren’t as well-known to users.” This code was the beginning of what he would one day create for Pandora.

Celma considers music more than his work. It’s his passion. He started playing the guitar at age 12. Around the same time, he developed a love of computer programming. Programmers write instructions that tell computers what to do. These instructions are called code. Celma studied computer science in college. After he graduated, he combined both his interests in his work.

“I built algorithms for recommending music,” he explains. Algorithms are sets of rules that a computer uses to solve a problem. Celma used them to improve the music his program suggested. He did that by including songs that weren’t as well-known. This code was the beginning of what he would one day create for Pandora.

Data-Driven Tunes 

Based on which music you choose, Pandora’s app predicts which other artists and genres you might like. Every time you use the app, you send more information for the algorithm to analyze. Celma and his team call these interactions “signals.” For example, if you skip a song, the app knows you didn’t like it. Or if you listen to an album on repeat, the app knows you really enjoy that artist.

“We get more than 1 billion signals each day from all our users,” says Celma. “This personalizes the recommendations based on your interests and your interactions with Pandora.”

Pandora’s app predicts which other artists and genres you might like. It does that based on which music you choose. Every time you use the app, you send it more information. Celma and his team call these interactions “signals.” For example, say that you skip a song. The app knows you didn’t like it. Or if you listen to an album on repeat, the app knows you really enjoy it.

“We get more than 1 billion signals each day from all our users,” says Celma. “This personalizes the recommendations based on your interests.”

MATH TALK

How is the number of “signals” a music app collects from its users related to the accuracy of its recommendations?

MATH TALK

How is the number of “signals” a music app collects from its users related to the accuracy of its recommendations?

Hands-on Math: Coding Without Computers

People need to give computers commands, called code, that tell computers what to do. Direct a “computer” to stack cups using a code made only of symbols. 

Materials

six plastic cups • plain white paper • pencil

Rules

• The stack of cups must be taller than one row of cups. 

• The “computer” does only what is written in code. 

• The code must include only the following symbols:

Procedure

STEP 1
Draw a diagram of what you want your stack of cups to look like. 

STEP 2
Brainstorm ideas about how to write directions to make the stack.   

STEP 3
Write out the directions using complete sentences. Could someone follow this easily? 

STEP 4 
On a new sheet of paper, change the sentences into code using the symbols above. 

STEP 5
Test your code: Give your code to a classmate. Can your classmate stack the cups to look like your diagram?

STEP 6
Evaluate the effectiveness of your code. If your code didn’t work, rewrite it and retest it by repeating steps 3-5. 

Hands-on Math: Coding Without Computers

People need to give computers commands, called code, that tell computers what to do. Direct a “computer” to stack cups using a code made only of symbols. 

Materials

six plastic cups • plain white paper • pencil

Rules

• The stack of cups must be taller than one row of cups. 

• The “computer” does only what is written in code. 

• The code must include only the following symbols:

Procedure

STEP 1
Draw a diagram of what you want your stack of cups to look like. 

STEP 2
Brainstorm ideas about how to write directions to make the stack.   

STEP 3
Write out the directions using complete sentences. Could someone follow this easily? 

STEP 4 
On a new sheet of paper, change the sentences into code using the symbols above. 

STEP 5
Test your code: Give your code to a classmate. Can your classmate stack the cups to look like your diagram?

STEP 6
Evaluate the effectiveness of your code. If your code didn’t work, rewrite it and retest it by repeating steps 3-5. 

Analysis

Compare your code with another studentʼs. Did anything work better? Why? 

Compare your code with another studentʼs. Did anything work better? Why? 

If you could create new code symbols, what would they be? Why would they be helpful?

If you could create new code symbols, what would they be? Why would they be helpful?

Why is it important for a computer program to have no mistakes in its code? 

Why is it important for a computer program to have no mistakes in its code? 

Algebraic Thinking
Multistep Problems
computer scientist

A scientist who studies computers and how they work
algorithms

Directions a computer follows to complete a task
preferences

Likes and dislikes
data

Facts or information used to make or calculate a value

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