The proverbial 'celestial jukebox' has become a reality. With today's online music services a music fan is never more than a few clicks away from being able to listen to nearly any song that has ever been recorded. Recommender systems can play a key role in this new music ecosystem, helping listeners explore, discover, organize and share music. However, in many ways music recommendation is very different than recommendation in other well-studied domains such as books and movies. In this talk we explore how recommender systems can be used in the music space, and the particular challenges that the music domain presents to the designers of recommender systems.

1. I have 10 million
songs in my
pocket.
Now what?
Paul Lamere
ACM Recommender Systems 2012 Photo (CC) by Jason Rogers

2. The challenge of music recommendation
A recommendation that no human would make
If you like Britney Spears ...
You might like the Report on
Pre-War Intelligence

3. The challenge of music recommendation
WTF - Why the Freakomendations?
Why do we see such bad
music recommendations?
Music is Special*
*of course every domain is special

4. The challenge of music recommendation
Why do we see such bad music recommendations?
Understanding the domain is
critical to the success of a
recommender

5. The challenge of music recommendation
Why do we see such bad music recommendations?
10 things to consider when
building a music recommender

6. #1 - Very large item space
10 things to consider when building a music recommender

7. #2 - Very low cost per item
10 things to consider when building a music recommender

8. #2 - Very low cost per item
10 things to consider when building a music recommender

9. #3 - Low consumption time
10 things to consider when building a music recommender
The average song length is around 4 minutes
E Book Reader: 24 books a year
Music subscriber: 25 songs a day
Pew Internet Project.

10. #4 - Highly Interactive
10 things to consider when building a music recommender
A typical music recommender ...
... in 1999, but not anymore

11. #4 - Highly Interactive
10 things to consider when building a music recommender
Today’s recommender
Recommendations are
integrated into
the listening experience

12. #4 - Highly Interactive
10 things to consider when building a music recommender
Today’s recommender
Minimal explicit feedback

13. #4 - Highly Interactive
10 things to consider when building a music recommender
Today’s recommender
Much Implicit Feedback
- Playing
- Skipping
- Repeating
- Adjusting the volume
- Sharing with friends
- Adding to a playlist
- Repeating the song
- Inspecting song info

14. #5 - Very high per-item reuse
10 things to consider when building a music recommender
songs[“as time goes by”].playcount += 1

15. #6 - Large personal collections
10 things to consider when building a music recommender

16. Personal Music Discovery Challenge
There’s a long tail in my iPod
Listener Study
Listeners 5,000
Average Songs
3,500
Per User
Percent of songs
65%
never listened to

17. #7 - Consumed in sequences
10 things to consider when building a music recommender
A good playlist is a balance of:
• Coherence
• Familiarity
• Discovery
• Variety
• Surprise
... in a pleasing order

18. #8 - Highly contextual usage
10 things to consider when building a music recommender

19. #9 - Highly passionate users
10 things to consider when building a music recommender

20. Let’s pause for a quiz
Why is this formula troublesome for
music recommendation and discovery?
(ΔMī¹=αΣDi[n][ΣFij[n-1]+Fexti[[n̄¹]])

21. Let’s pause for a quiz
Why is this formula troublesome for
music recommendation and discovery?
Because it is the name of a
song by Aphex Twin
(ΔMī¹=αΣDi[n][ΣFij[n-1]+Fexti[[n̄¹]])

22. #10 - OMG Metadata
10 things to consider when building a music recommender
The The
Duran Duran Duran
!!!
†††
///▲▲▲
▼□■□■□■
Various Artists

23. #10 - OMG Metadata
10 things to consider when building a music recommender

24. Music Taste is Irrational
The challenge
Music Music
I Like You Like
Music
I Used
To Like
Get this t-shirt at dieselsweeties.com

25. I have 10 million
songs in my
pocket.
Now what?
Paul Lamere
Paul@echonest.com
MusicMachinery.com
@plamere
Photo (CC) by Jason Rogers