How to tighten the timing of audio in the Reaper DAW. Using stretch markers to improve the playing and timing of a recorded piano piece. Recorded on a 1930s Berlin built Steck upright piano to a click track. By adding Reaper stretch markers to the main transients you can move parts of the recorded audio to tighten up the timing to the grid or beat. To manually add a stretch marker place the cursor where you want it to go on the wave form within an item – usually just before transient (highest / loudest part of the waveform) and click while holding down option/alt and cmd/ control. To remove a stretch marker – option or alt click it.