Overdubbing means recording a new performance on top of one that is already recorded. With MIDI you can add new notes while keeping the existing ones, which helps when you build a drum pattern or a chord part little by little. Depending on the device or the DAW, the word is also used for stacking another audio take.
Adding without erasing what is there
Depending on the settings, normal recording replaces the existing content. When overdub is enabled, new input is added to the MIDI notes already there. You can record the kick first, add the snare on the next pass, then add the hi-hat.
Using it with MIDI
It suits adding another note to a recorded chord, adding ornaments to a bass line, or layering drums played on pads. Set a loop range and play it repeatedly so you can add a little more to the same section each time. Quantize afterwards if you need to tidy up the timing.
How it differs from replace recording
Overdubbing keeps the existing data and layers on top of it, while replace recording swaps the content of a set range for the new recording. If you only want to fix part of a take, punch in and punch out or another take are also options. Check the record mode against what you are trying to do.
Things to watch out for
When notes of the same pitch overlap, some instruments get louder or sound unnatural. Clean up unwanted notes in the piano roll. Play back in short sections as you go so you do not lose track of what you have added.
How it relates to comping
Overdubbing is a way of stacking performances, while comping is a way of assembling the best parts from several takes. Choose based on whether your goal is to layer or to select. For the basics of MIDI recording in a DAW, see the article on DAWs.
