Controlling the speed of evolution. This can either be applied globally to all parts of the spectrum, or individually in which case the different portions of the spectrum phase against each other. An extreme and interesting case is to freeze on a single FFT frame.

Adjusting the ratios within spectral subsets. This feature which might be described as ‘spectral companding’ creates a warping effect on the spectrum (and formants if any).

Locking all oscillators to the frequency evolution of a selected bin, according to a data set of transpositions, to ‘harmonize’ the selected oscillator.

Selecting a non-sinusoidal waveform for resynthesis – a distortion effect adding many harmonics to the spectrum.

Triggering autonomous algorithmic traversal schemes. This allows the performance to proceed in unpredictable ways, especially with behaviors which would be difficult or impossible for a human performer to produce. Further, it should be noted that with the 7 bit resolution of MIDI ‘continuous’ controllers, it is impossible to smoothly navigate analysis sets containing more than 128 frames. (Ours contain several thousand frames.)

Network Distribution with UDP Packets

The computer running the midiroute program encodes MIDI control data into tagged numbers which are then broadcast to the local network. Each datum is sent through a UDP (User Datagram Protocol) packet to its broadcast destination. Each UDP packet is encapsulated into one ethernet packet under normal conditions and therefore the UDP packets should be received simultaneously by each computer in the local network. This mechanism may be extended into the worldwide network.

In order to communicate with groups of computers in different network locations, we add a relay computer for each group. This relay computer receives IP packets from the midiroute computer and broadcasts UDP packets to its local network.

Latency, Synchronization Error and Bandwidth

Latency is the delay time between actual performance gesture input by the performer and the change of sound in the space. Latency must be kept as low as possible in a musical performance system. In our system, the average latency is around 100 msec. The main source of latency is an eight kilobyte sound output buffer in the Windows environment. The impact of other sources of latency, such as network delay or re-synthesis delay, is marginal. Sound output latency should improve with newer generations of sound hardware.

Synchronization error is the difference in latencies within a group of computers receiving the same control data. If the differences are low, errors are noticed as spatial effects (randomized delays between channels) as heard in our system, but if