Tutorials and Topics - Peabody Computer Music

How MSP WorksMax patches and theMSP signal networkRealtime sound synthesis of this complexity on a general-purpose personal computer waspretty much out of the question until the introduction of sufficiently fast processors suchas the PowerPC. Even with the PowerPC, though, this type of number crunching requiresa great deal of the processor’s attention. So it’s important to be aware that there arelimitations to how much your computer can do with MSP.Unlike a MIDI synthesizer, in MSP you have the flexibility to design something that is toocomplicated for your computer to calculate in real time. The result can be audiodistortion, a very unresponsive computer, or in extreme cases, crashes.Because of the variation in processor performance between computers, and because of thegreat variety of possible signal network configurations, it’s difficult to say precisely whatcomplexity of audio processing MSP can or cannot handle. Here are a few generalprinciples:• The faster your computer’s CPU, the better will be the performance of MSP. Westrongly recommend computers that use the PowerPC 604 or newer processors. OlderPowerBook models such as the 5300 series are particularly ill-suited to run MSP, andare not recommended.• A fast hard drive and a fast SCSI connection will improve input/output of audio files,although MSP will handle up to about eight tracks at once on most computers with notrouble.• Turning off background processes (such as file sharing) will improve performance.• Reducing the audio sampling rate will reduce how many numbers MSP has tocompute for a given amount of sound, thus improving its performance (although alower sampling rate will mean degradation of high frequency response). Controllingthe audio sampling rate is discussed in the Audio Input and Output chapter.When designing your MSP instruments, you should bear in mind that some objectsrequire more intensive computation than others. An object that performs only a fewsimple arithmetic operations (such as sig~, line~, +~, -~, *~, or phasor~) iscomputationally inexpensive. (However, /~ is much more expensive.) An object thatlooks up a number in a function table and interpolates between values (such as cycle~)requires only a few calculations, so it’s likewise not too expensive. The most expensiveobjects are those which must perform many calculations per sample: filters (reson~,biquad~), spectral analyzers (fft~, ifft~), and objects such as play~, groove~, comb~, andtapout~ when one of their parameters is controlled by a continuous signal. Efficiencyissues are discussed further in the MSP Tutorial.34