The volume meter at the top of Renoise. Do I need to make sure that thing doesn’t turn red? Does that mean there’s not enough headroom?
Yes very evil. No, as long it sounds good… It’s hard clipping then. Instead you can limit, compress or soft clip at master bus, but do this only after your song sounds already good and complete without it. If your song sounds too quiet if you enabled auto volume on master bus, you have too loud transients (I usually have). Transients are very tricky, because they can sound good on one speaker system, but crap on the other. So don’t trust too much on one speaker system here. Another trick is to listen to the track very very quiet with headphones. I mean so quiet you hardly can hear much. Then you will hear, if there are obviously too loud transients, or too loud bass. This is the second point: bass frequencies use much more energy/headroom than highs. So a mix that has not so much bass, but lot of high freq can of course be much much louder without clipping. But u need to keep a balance of all frequencies. Load any favorite song that you think it sounds very good into renoise as sample. Play this song on c-4 on a track without fx. Now watch the frequency analyzer. I recommend you to use here the following settings: 16384 window size, falloff speed quite fast, slope 4db. You will see that your favorite song is almost a flat line on the graph. So this is the target you should try to reach by make a good volume and frequency balance of your mix. Compress the instrument tracks themselves, so no one will spike out too much with transients. Since bass has the most energy, especially take care on those tracks.