Without pretending to be an expert on the subject of music-theory or audio-processing, my n00b'ish doubt is -- MIDI, unlike MP3 would be devoid of voice... and in my overtly simplistic thinking -- presence / absence of which (i.e. voice) could be a "brute-force" way of detecting refrain/chorus ... unless a lot of "grammar" (i.e. semantic constraints) of music-theory are enforced, and I am afraid such a grammer could only be made for a small subset of a particular genre at best. IMHO, some heuristics could be used to "train" a statistical model, to identify refrain sections, s.a. a Bayesian model. You use some heuristic parameters to detect refrain, and then use a large corpus of human responses to validate the identification, there by tuning the model.
On Tue, Nov 4, 2008 at 3:11 PM, alex23 <[EMAIL PROTECTED]> wrote: > On Nov 4, 2:20 pm, Joe Strout <[EMAIL PROTECTED]> wrote: > > We've got a need to generate short "samples" of songs that are in MIDI > > format, to provide a preview function in a web app. We'd like to do > > something more clever than just taking the middle 20 seconds (or > > whatever) of the song -- ideally, we'd like to find the chorus, since > > that's likely to be the most easily recognized part of the song. > > > > I believe this could be done fairly reliably by looking for patterns > > in the MIDI file, though I'm sure there are plenty of complications to > > this simple idea. > > My first thought is that would be incredibly difficult, but a quick > google search pulled up a couple of papers: > > "Music Scene Description Project: > Toward Audio-based Real-time Music Understanding" > http://ismir2003.ismir.net/papers/Goto.PDF > > The RefraiD (Refrain Detecting Method) detects sections > being repeated and identifies the chorus (refrain) sections > of songs in popular-music CDs. Most previous methods > detected as a chorus a repeated section of a given length > (Logan and Chu, 2000; Cooper and Foote, 2002) and had > difficulty identifying both ends of a chorus section and > dealing with modulations (key changes) (Peeters et al., > 2002; Dannenberg and Hu, 2002). By analyzing relation- > ships between various repeated sections, RefraiD can de- > tect all the chorus sections in a song and identify both > ends of each section. It can also detect modulated chorus > sections by introducing a similarity measure that enables > modulated repetition to be judged correctly. > > The paper doesn't go into much detail beyond that, but does refer to > more that do. > > "A chorus-section detecting method for musical audio signals" > > http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?tp=&arnumber=1200000&isnumber=26996 > > By the same authors, I believe. Although they're talking about audio, > I would expect the technique used could be readily applied to midi as > well (probably more easily, in fact). > > Note that: "Experimental results with a popular-music database show > that this method detects the correct chorus sections in 80 of 100 > songs." So it's going to be wrong 1 in 5 times, if that's an > influencing factor in trying to do this programmatically. How many > MIDI files are you talking about here? Could it be easier to just > manually mark the chorus for each? > > > 2. Anybody have an interest in music theory, as well as mad Python > > skills? Want a paying contract job? If so, please contact me off- > > list. I'd enjoy pursuing this myself, but if you think you can do a > > better job at a reasonable rate, I'm happy to let you do so. > > Give me a few days to see what my upcoming schedule is like and I may > get back to you on this. I have a friend who has worked on > computationally generating emotional expression with MIDI just > recently, I'll pass this on to him as well. > > Is Python a strict requirement for this? > -- > http://mail.python.org/mailman/listinfo/python-list > -- regards, Banibrata http://www.linkedin.com/in/bdutta http://octapod.wordpress.com
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