In the context of music perception, for instance,
the capacity of detecting gradual tempo changes is
fundamental.
...this comparison will be made in a context
where relative sensitivity to accelerations and
decelerations is tested. This relative sensitivity is
argued to be related to the fundamental frequency of some
oscillating process (Vos et al., 1997).
Performing gradual tempo changes gracefully as
well as accurately is quite demanding, particularly in ensemble
playing.
Synchronization becomes a more demanding task
when the metronome’s tempo changes systematically. In
this case, phase correction alone is not sufficient for keeping
synchrony. Rather, the internal timekeeper must be
adjusted to the changing period of the metronome. Several
models have been proposed for period adjustment. Mates (1994a,
1994b) has suggested that timekeeper adjustments are based on the
discrepancy between the current timekeeper interval and the
previous metronome interval. This error signal is used to adjust
the timekeeper by adding or subtracting a fixed proportion of the
interval difference. A simple alternative that we pursue in this
article is that, like phase, the timekeeper period is adjusted on
the basis of the asynchronies, that is, the temporal difference
between perceived events, rather than the difference between time
intervals.
In the experiment reported, we observed a novel
phenomenon: When synchronizing with a metronome that undergoes
accelerando or ritardando, the synchronization errors follow a
systematic pattern in the transient phase, which held for all
subjects. If the initial and final tempi differ widely,
subjects first undershoot the smoothly changing tempo, then catch
up and overadjust twice before settling on the goal tempo. The
question is whether linear period-adjustment models are compatible
with such data patterns. Surprisingly, a new version of the
highly successful two- level phase-error correction model
(Pressing, 1998; Vorberg & Wing, 1996; Vorberg & Schulze,
2002) fared rather well. Based on the assumptions that
(1) local phase adjustments and global period adjustments are
active simultaneously during noticeable tempo changes, that (2)
both mechanisms are fed by the same error information, and that (3)
adjustments are first-order linear, the model accounts for the
qualitative data pattern quite well, although quantitative
goodness-of-fit leaves much to be desired. However, even the
qualitative fit was satisfactory only when restricted to the
transient phase of the data, which implies that there must exist
additional control mechanisms that determine when the period
adjustment mechanism is started and stopped (e.g., by setting the
period correction gain).