\section{The Relationship Between Concert and Usage Behavior\label{sec:both}}

The last.fm music service records listening behavior of songs that have appeared in some published form, such as studio albums, singles, and recordings of live concerts. The Grateful Dead deviated from the standard model of releasing studio albums, in that their primary revenue stream was through concert performances, even from the start. The Grateful Dead produced 13 studio albums and 77 live albums.  The band's first live album, \album{Live/Dead}, was released in 1969.  With respect to the influence of live recordings on the present generation of listeners, nearly all live albums were a direct reflection of a particular live concert performance and as such, respected that concert set list's song sequence. Thus, if a last.fm listener were to listen to any one of the many live albums, he or she is, in fact, replaying concert history and contributing proportionately to the number of songs listened to as times played in concert. This notion is further accentuated by fans that created digital renditions of their favorite concert tapes.\footnote{Prior to the advent of the Internet and the easy distribution of digital audio files, Grateful Dead concert tape trading was an extremely popular way of disseminating the Grateful Dead's live experience. In fact, the band encouraged this \cite{tapers:dwork1998}. Many tapes have now been digitized and shared online by fans.} Given that there are currently 5 times more live albums than studio albums, one may expect that last.fm users would primarily listen to recordings of concerts and that the usage data would be directly correlated with that of the set list data.  However, as shown in this section, there are significant deviations from a perfect correlation.  Reasons for these deviations may include the fact that listeners can replay only their favorite songs from live albums, may prefer studio albums to recordings of live shows, and are able to make compilations of tracks (``playlists'') that differ from the live and studio productions.

Figure \ref{fig:usage-plays} plots each song in a two-dimensional space. Each song is provided a coordinate in this space, where the horizontal coordinate is the number of times the song was played in concert and the vertical coordinate is the number of times the song was listened to by last.fm members.