Tutorials and Topics - Peabody Computer Music

Tutorial 20: MIDI control—SamplerBasic sampler featuresIn this chapter we demonstrate a design for playing pre-recorded samples from a MIDIkeyboard. This design implements some of the main features of a basic sampler keyboard:assigning samples to regions of the keyboard, specifying a base (untransposed) keylocation for each sample, playing samples back with the proper transposition dependingon which key is played, and making polyphonic voice assignments. For the sake ofsimplicity, this patch does not implement control from the pitchbend wheel or modwheel, but the method for doing so would not be much different from that demonstratedin the previous two chapters.In this patch we use the groove~ object to play samples back at various speeds, in somecases using looped samples. As was noted in Tutorial 19, if we want a polyphonicinstrument we need as many sound-generating objects as we want separate simultaneousnotes. In this tutorial patch, we use four copies of a subpatch called samplervoice~ tosupply four-voice polyphony. As in Tutorial 19— we use a poly object to assign a voicenumber to each MIDI note, and we use route to send the note information to the correctsamplervoice~ subpatch.poly assigns a voice number to each MIDI note, to send information to the correct subpatchBefore we examine the workings of the samplervoice~ subpatch, it will help to review whatinformation is needed to play a sample correctly.1. The sound samples must be read into memory (in buffer~ objects), and a list of thememory locations (buffer~ names) must be kept.2. Each sample must be assigned to a region of the keyboard, and a list of the keyassignments must be kept.162