We recently released a new way to talk in Cocoon, designed to avoid the disruptiveness and inflexibility of a phone call. Spontaneous audio/video, keyed off in-app presence.

A unique feature like this offered me the opportunity to craft custom alert sounds. Here's a thread:

UI sound design has quietly become a vast discipline. Many apps have custom tones, and large companies have entire teams devoted to the craft.

I have audio experience, but had never shipped any UI sounds before. Rather than jump into Logic, I started plinking around on the piano

The piano takes your tones down a musical path, which isn't a given; a viable alternative would be neutral sounds like wood knocks, squishy plops, click snaps etc.

What I prefer about musical tones, is how much more control you have over the emotional quality of the tone.

Once I had some sequences I liked, I drew them in Logic and tried out different sounds. My internal brief was "squishy radio – what would a beep sound like on a radio made of clay".

This was a good start, but most of these explorations were too subdued when played back on device

I eventually landed on a bell-like synth, which combined a soft ding, with a hard click. This worked best on device, as the top-end click could push out of a pocket, and the midrange tones could carry the tune.

The first sound I made was our in-app invitation notification.

I wanted it to to feel like an open ended question – not at all resolute or complete – more like the sonic interpretation of a pondering ellipsis ("i wonder...")

Our join and leave sounds are standard two-tone intervals, rising for joins and falling for leaves.

For the latter, I toyed with more woeful departure sounds, but certain sequences sounded too much like errors, so I kept it pretty stoic – a musical 'k bye'.

Probably the most important sound is the iOS notification sound (what you hear if your phone is locked).

I spent a while dialing in a unique sequence that combined high and low frequencies, had a recognizable/repeatable melody, and still maintained a short overall duration.

Beyond sound, this feature has tons of great details, like the custom audio reference animation built by @pixelmatrix and @dyah10

You can read more about all of this here: https://cocoon.com/talk.html