A short two-note warning that rises instead of falling, so it reads as "careful" rather than "no". Soft triangle wave, no harsh edge, audible on laptop speakers at low volume. Use it for unsaved changes, low battery, a form field about to expire, or any alert that wants attention without alarm.
two triangle notes, a perfect fifth apart: G5 659 Hz for 110 ms, then 125 ms of silence, then B5 988 Hz for 190 ms envelope: 4 ms attack, 100 ms decay on the first note, 170 ms on the second no filter needed: triangle already has weak harmonics seam: single shot, buffer 0.29 s (the second note is inaudible by 240 ms; no silent tail)