A great way to overcome the ‘16-bar loop problem’ is to create a rough song template before you even begin creating any sounds. Do this by creating empty MIDI clips across your DAW’s arranger for each major track element, sketching out a map of how you expect your song to progress. This doesn’t have to be a final arrangement you end up sticking to rigidly, but it will be much easier to ‘remix’ this rough idea than start with a totally empty timeline.
An easy method for creating these kinds of templates is to base them around a reference track. Drag one of your ‘placeholder’ reference tracks onto your DAW’s timeline, and follow the steps below to create – and reshape – a template from it.