The Quest for Musical Genres: Do the Experts and the Wisdom of Crowds Agree?

ISMIR / Philadelphia, US // September, 18th 2008

The Quest for Musical Genres:

Do the Experts and the Wisdom of Crowds Agree?

Mohamed Sordo, Òscar Celma, Martin Blech, Enric Guaus(Music Technology Group ~ UPF)

ISMIR / Philadelphia, US // September, 18th 2008 // òscar celma // MTG / UPF

motivation

taxonomy (controlled vocabulary)


motivation


folksonomy (free text)


motivation


VS. folksonomy (free text)


expert-based

• taxonomy Mp3.com 2005


expert-based

• taxonomy 13 seed genres (components) 7 levels 711 genres

Rock Hip-Hop


community-based

• folksonomy last.fm


community-based

• folksonomy last.fm ~137K artists ~90K tags (after cleaning)


outline

1) Mapping tags to genres

2) Computing similarity among genres

3) Agreement between experts and wisdom of crowds

4) Reconstructing the taxonomy from the folksonomy


1) mapping tags to genres



• folksonomy ~ taxonomyJade (artist tags):

90s, illinois, new jack swing, rnb, r and b,

urban, ...




R&B, New-Jack-Swing, Urban




R&B, New-Jack-Swing, Urban

(39% tags matched

with MP3.com genres)


outline






2) computing similarity among genres

• Taxonomy distance(Doo-Woop, Urban) = 3

Penalty when crossing components distance(Urban, Rock-Pop) = 7


2) computing similarity among genres

• Folksonomy LSA (SVD), 50 dim.

Cosine similarity sim(Urban, Doo-Wop) = 0.868 sim(Urban, Pop-Rock) = -0.145


outline






agreement experts ~ wisdom of crowds

• 1) Separate (taxonomy) genre components using (folksonomy) genre sim. intra-component similarity inter-component similarity

• 2) Correlation between (taxonomy) genre path distance and (folksonomy) genre sim. DistanceTAXONOMY(g1, g2) ~???~ SimFOLKSONOMY(g1, g2)



• 1) intra-component similarity, using LSA




Alternative-Rap

Dirty-Rap

West-Coast

Hip-hop

Bass-Music




Blu

es

Hip

-hop

Rock

/Pop

Ele

ctro

nic



• 1) inter-component similarity centroid for each component



• 1) inter-component similarity Clearly distinguishable from the rest

Hip-hop, Blues, Jazz

Relationships found Country ~ Bluegrass (~ Folk) R&B-Soul ~ Gospel/Spiritual Electronic/Dance ~ Vocal/Easy-Listening New-Age ~ World/Reggae (!)



• 2) taxonomy genre distance vs. folksonomy genre sim.

West-Coast

Calypso



• 2) taxonomy genre distance vs. folksonomy genre sim. DistanceTAXONOMY(West-Coast, Calypso) = 8

West-Coast

Calypso



• 2) taxonomy genre distance vs. folksonomy genre sim. DistanceTAXONOMY(West-Coast, Calypso) = 7 SimFOLKSONOMY(West-Coast, Calypso) = 0.04

West-Coast

Calypso



• 2) taxonomy genre distance vs. folksonomy genre sim.


outline






reconstruct taxonomy from folksonomy

• Select closest parent, using folk. genre sim. Get genres at level n



• Select closest parent, using folk. genre sim. For each genre at level n



• Select closest parent, using folk. genre sim. Get all nodes at level n-1 (possible parents)



• Select closest parent, using folk. genre sim. Compute cosine LSA similarity



• Select closest parent, using folk. genre sim. Assign closest parent



• Select closest parent, using folk. genre sim. Compare with taxonomy parent



• Results


...and also!

• MIREX 2007 results (Team: IMIRSEL-M2K SVM)

RAPHIPHOP 84.05%BLUES 77.68%EDANCE 77.68%JAZZ 72.53%COUNTRY 71.37%ROCKROLL 69.53%BAROQUE 65.81%METAL 61.11%ROMANTIC 52.79%CLASSICAL 33.33%


conclusions

• Consensus in some genres expert, community, and audio

• Discovery in terms of taxonomy/folksonomy coarse / fine grained static / dynamic

• Taxonomy adapts according to the folksonomy

• Do we need experts?

• Are some (wisdom-of-crowds) shepherds more experts than “THE” experts?


future work

• Use more taxonomies and folksonomies

• Agreement measures

Uncovering affinity of artists to multiple genres from social behaviour data (Claudio Baccigalupo, Justin Donaldson, Enric Plaza)

ISMIR / Philadelphia, US // September, 18th 2008

THANKS!!!

Mohamed Sordo, Òscar Celma, Martin Blech, Enric Guaus(Music Technology Group ~ UPF)

The Quest for Musical Genres: Do the Experts and the Wisdom of Crowds Agree?

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