On November 20, 2009, drew Roberts wrote:
> On Thu, Nov 19, 2009 at 9:06 PM, Gordon Haverland
> 
> <[email protected]> wrote:
> > On November 19, 2009, Clint Adams wrote:
> >> On Fri, Nov 20, 2009 at 12:36:56AM +0100, Maciej Łoziński 
wrote:
> >> > What is the state of the recommendation/stats engine of
> >> > libre.fm? I made a quick look at the code, and haven't
> >> > noticed anything in subject. Is anyone
> >> > coding/designing/thinking of it at the time?
> 
> snip
> 
> > We can observe correlations between people's complete
> > libraries, which I believe (with no proof) is what Last.fm
> > does.  We could look at the time series of songs that people
> > listen to: what is the probability that a person wants to
> > listen to classical music within N different songs?
> 
> If we want to do something like this right, will we not need
>  some player cooperation? A toggle to send along info as to
>  whether this series of plays is from a personally hand ordered
>  playlist or not. (personally chosen order versus randome,
>  computer chosen or "other" chosen of some sort.
> 
> snip

I think it would be useful to know whether the scrobbling is 
coming from a hand ordered list, from some music player's idea of 
random, or from some external source.  Supposedly a hand compiled 
list what not see the user skipping to the end of a song.  For 
using some music player's definition of random, you might find 
users more often skipping to the end of song.  In listening to an 
external source, the only thing which comes to mind is the 
Love/Hate tags which Last.fm uses (or used to use).

Do any music players give information on music sources?  How many 
have Love/Hate options?


Gordon Haverland pisze:

> It's great that you spent some time on sharing your
> thoughts though. I wish you success in finding great job as
> soon as possible.

Me too.  I'm starting to notice that people are finding more 
obtuse than usual, which is not a good thing.  I don't like to be 
seen that way.

>> You aren't asking about playing music randomly, but I
>> will start there.  If you ask 20 people about how they
>> define random plays of music, you will probably get
>> somewhere between 10 and 20 different definitions.  And all
>> of them are correct.

> Doesn't just random mean random? What do you exactly have
> on your mind?

Some people think of shuffling a deck of cards when playing
songs at random.  One idea of random is we shuffle the deck 
(well).  We then draw songs in order until the deck is exhausted.
In that version, there is no probability of playing the same song 
more than  once, unless that song occurs in the person's 
collection more than once.  In that situation, it is possible that 
the same song can be played multiple times, one after another.

Another option is drawing cards at random, with replacement.  We 
draw a card (song) and start playing it.  We then put the card 
back in the deck, and reshuffle.  This mechanism never ends (the 
deck is never exhausted).  Again, we have the probability of 
listening to the same song back to back, with one different song 
in between, ....

We can incorporate nearest neighbour correlations, if song A 
plays, it makes it unlikely that B plays next and it makes it 
likely that C plays next.  This can get carried to higher and 
higher order correlations.

There are some albums which tell a story across all the songs of 
the album.  Imaginos by Blue Oyster Cult comes to mind.  If in the 
course of drawing songs at random, what happens if I draw a song 
from that album?  Do I want to play the entire album in order?  Do 
I want to play from that song to the end of album in order?  Do I 
want to just play that song?  What happens if the next draw (the 
draw after, the draw after that, ...) is from that same album?

As I said, there are lots of things involved in playing songs "at 
random" that people can take issue with.

>> If we look at how people want to listen to music,
>> their listening habits are seldom that simple.  You can
>> find people who enjoy both hard rock and classical, but if
>> they decide to listen to hard rock, they do not want to
>> have their playlist suddenly jump into classical.

> Yes, but *generally*, such jumps are rare, and when you want
> to listen to "hard rock" om last.fm, you get mostly hard
> rock, and when you get something that you don't want to
> hear, you just click "next".

I suppose if you are listening to the tag "hard rock" that won't 
happen.  But if you listen to user fortran2's radio station 
(currently at 347446 plays), you are going to find jumps because I 
listen to classical, country, rock, folk, jazz, blues and some 
other stuff.

>> To consider text, some people are interested in
>> constructing  "random text".  Perhaps a good example for
>> more complicated text  construction is Lorem Ipsum. 

> I don't get what text has to do with music. Or is it some
> sort of parallell?

Building things at random is all inherently the same process.  It 
doesn't matter whether you are making random integers, random 
float points that are uniform 0-1, or anything else.  But 
applications such as random text and random music have 
expectations (correlations) that people may want to use.  But 
working with extended correlations does come with a computational 
burden.  You need to draw more than one random number to find the 
next song.  But time consuming part is comparing the other random 
numbers to complicated probability functions in order to decide 
yes or no (or to pick a song).

>> We can observe correlations between people's
>> complete libraries, which I believe (with no proof) is
>> what Last.fm does.  We could look at the time series of
>> songs that people listen to: what is the probability that
>> a person wants to listen to classical music within N
>> different songs?  If N is small, there is a small
>> probability that that they might want to listen to a
>> classical  song.  We could construct listening
>> recommendations based upon N=1  (next song to be listened
>> to), N=2 (1 song after the next song),  and so on.  We
>> could look at these correlations when restricted to
>> certain tags (we don't consider the probability of listening
>> to Alice Cooper N songs after listening to Vivaldi).

> Do you mean when somebody listens to a classical track,
> he'll probably want to listen to another one? If so, that's
> sort of I was thinking also.

Sorry, I'm getting obtuse here.  If someone is looking for 
recommendations on rock, the fact I listen to stuff other than 
rock shouldn't preclude my listening habits from being useful.

If what goes into recommendations is only the songs themselves, 
this is easily done.  If a person is looking at correlations 
between songs (what is the probability of hearing Don't Fear (The 
Reaper) immediatley after listening to Sharp Dressed Man), then 
people whose listening habits  cross gendres can introduce 
problems.  Immediately after isn't as much a problem as one (or 
more) song in between.  Because the person looking for 1 song 
inbetween correlations, isn't expecting The Four Seasons by 
Vivaldi as the song in between.

>> The above is handwaving theory.  If we look at music
>> statistics  from the music business over the last N years,
>> we run into  problems.  If you listen to TOP-40, you
>> will (almost?) never run  across a country/western song.
>> If you look at music sales  statistics, there is an
>> overlap between Top-40 and  Country/Western.  

> What kind of overlap are you thinking about? That people who
> buy top-40 buy also country and western?

Probably being obtuse again.  There are false statistics out there 
as well.  And the split between Country/Western and Top-40 is a 
good example.  I think there are a number of people who listen to 
Top-40 and hate Country/Western  because they have been 
conditioned to think that way.  And I think there are a number of 
people who started listening to Country/Western because they 
wanted to be different (not following the masses by listening to 
Top-40).  Should recommendations try to bridge the gap?

There are a few songs that have made the top of the charts in both 
Top-40 and Country/Western.  Those songs probably make good 
recommendations.  If they are open to that, they may eventually 
find parts of the "enemy" gendre that aren't that bad.  Not that I 
think many Top-40 people are going to be listening to "John Deere 
Tractor".  But they might find enjoyment in THE TRUCK GOT STUCK  
by Corb Lund.  It probably helps a little if they live somewhere 
on the Great Plains however (lots of people don't know about the 
genetically modified canola varieties like Roundup-Ready Canola 
that exist).

> When somebody doesn't want to listen to country/western,
> that's ok for me. I don't think we have to deal with that,
> even if maybe it's irrational. But also it's very possible
> that neither top-40 listeners nor country/western listeners
> will come across libre.fm ;-)

Actually, I think that the "better DJs" (at radio stations) out 
there would probably do well to have their playlists entered as 
users at Libre.fm.  And then they would be able to get 
recommendations of other songs to play, instead of just pushing 
whatever the music people want pushed that week.  :-)

I'll have to think about your second note a bit Maciej.

Take care.
Gord
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