Is there a way in Renoise to combine several samples into one, with each one having a different keyboard key ? This can be used for instance to combine several samples of various percussion so that they can be played at once from a keyboard. Or to combine several instrument samples, each sample being a different note of the same instrument.
You mean put a bunch of samples into the same instrument (XRNI)? You can just drag and drop individual samples into a single instrument from the disk browser (lower right). Any single sample can be put on any key (or range of keys), can be layered to trigger either simultaneously or in a random or successive order. Just maybe have a look at the Instrument section of the documentation, it covers how to make instruments (including multi-sample instruments). Or look in the Downloads section and check out some of the bigger (multi-sample) instruments there. Renoise’s style of instrument making is pretty similar to a lot of samplers, really.