A technique in which a single patch in a sampler or sample playback synth is composed of multiple actual samples, which are assigned to different portions of the note span. This technique is often used to improve the realism of samples of conventional instruments, many of which have timbrel properties which are different between higher and lower notes. By limiting how far a given sample has to be pitch shifted up or down to play a selected note, the timbrel properties of a played note are kept closer to how the note sounds on the instrument that was sampled. As an example, a performer making a patch for a sampled saxophone might choose to sample every fifth note in the instrument's chromatic scale, so that each sample will be assigned to a span of five notes. If a given sample is that of an F played on the sax, the sample could be assigned to Eb, E, F, F#, and G, so that if any of these notes are played on the synth, the F sample will be used, appropriately pitch shifted for the played note. The next sample down would be recorded at C, and used to play D, C#, C, B, and Bb, and so on up and down the instrument's range.
Another use of multisampling is to build a "drum kit" consisting of a number of drum and percussion sounds which are all accessible via a single patch selection. In this method, usually each drum or percussion instrument sample is assigned to a single note; that drum sound is then re-created by playing the appropriate key on the synth's keyboard. A set of drum pads can then be set up so that each pad is assigned to the MIDI note number of the desired drum sound, so that each pad plays a different instrument.
Compare to velocity switching, another technique that is frequently used to add realism to the sound of sampled conventional instruments.