Page  140 ï~~Tracking Musical Beat Paul E. Allen and Roger B School of Computer.; Carnegie Mellon Un Pittsburgh, PA 1521': email: Paul.Aflen@, Roger.: ABSTRACT: Identiyn Observing the temporal previous locatic atteir musical SuL. that constraind to hold a single current notion of beai they will fail predict beats and not recover 1 mistake is made. We propose a new model that u, interpretations the perform ance. any 6i placement are made according the most c red considerati on.

Page  141 ï~~rPelime method. We were dissatisfied withispro sensitive enoui tempo changes, causing errors. responsive tempo changes we parameterized the L: expectation of meig able find parameter values U performance. The on history mechanism uses previous tempos. The decay rate has a direct affect oi tracker.j respect t unstable. one extreme, 100% data, decay, the tracker wi. the latest note allowing rapid tempc track At the other extreme, 0% decay, the with the present state so that consideration of the int The decay rate is one parameter we studied. The second parameterization applies to the co indicate the cetaint wit which the beat tracker b: downbeat an4 thus, indirectly, the amount the tempo s original confdence function sawtooth function I downbeats and minimum value of 0.0 at points exacil downbeats; its slope is either 10l or -1.0. We took thi itto an exponent parameter (thus with a parameteri --4 4 - - L- -! ' _- I At - N a-- -1- -- A

Page  142 ï~~interpretations that do not make musical sense are disc remain become the new active states for the next expansi note ornate 24.0 sec. input mt position: 20 beat period: 1.2ws beat phase: 24.0 i inter-onset interval: 0.9 sec. perceive (tempo decrease) / perceive (tempo increase) rmetric position: 20.5 beat period: 1.8 soc. rmti position: 21. beat period: 0.9 si+ atphase: 25.8 sec Jba phase: 24.9 E Figure 1: S.mlfe example og Because this is a real-time method and the numl 11iherallv nnnlv flflflfl techninuetot decrease the ma! lan it I - S * *

Page  143 ï~~jyuinote onset infra-onset interval) Current Active States Branching Factor Limit (pruning method 4).. - -....., S... I * *.... - *...........,.....,............ I *.. I * *.. I *. ~... 00 r k+i Sl,.': Unmusical Interpretation (pruning method 1) State Combinaton (prnng method 3) J tli most credibile -A- - 1' - - L - A -a / N l