Starting with this view: … double-click inside the yellow to bring up the midi editor. Then, decide what source area you want to copy from, and as shown in the picture below, right click a corner of the source area, drag a rectangle, and release: After you have dragged the rectangle, you will have this, that is, the selected area is now highlighted: The action of copying and pasting is then done in one go (in contrast to the the normal Windows actions where ctrl-c puts the selection into the clipboard, and ctrl-v pastes it elsewhere), by holding down the Ctrl key, hovering over one of the selected items until the cursor changes to a pointer with a plus symbol (I can’t show that symbol right now), and then dragging the block to its destination: Now, people who use Reaper every day might well say it is all in the manual, but I find it is not at all obvious, given the absence of diagrams on this. The specific challenge I find is pasting stuff from the clipboard – it pastes to the end of the song, and not to any obvious place I can understand. When I need to master that, I’ll update this. Quanitization Unless you truly have a mass of notes that are off, I prefer dragging notes to the right place, as to my ear, quantization does something weird to the quality of the notes. So if I do have a mass of notes… But I couldn’t even find where to quantize in Reaper at first. Again it is down to the midi editor, so drill into that again. In the editor you have the toolbar, which by default contains an icon for quantization: Click on that, and you get this: That is all I have to say about quantization at this point – I just wanted to know where it was.