The classic Macintosh startup sequence includes hardware tests which may trigger the startup chime, Happy Mac, Sad Mac, and Chimes of Death. On Macs running macOS Big Sur or later the startup sound is enabled by default, but can be disabled by the user within System Preferences (Big Sur or Monterey) or System Settings (Ventura).
The Macintosh startup chime is played on power-up, before trying to boot an operating system. The sound indicates that diagnostic tests run immediately at startup have found no hardware or fundamental software problems. The specific sound differs depending on the ROM, which greatly varies depending on Macintosh model. The first sound version in the first three Macintosh models is a simple square-wave "beep", and all subsequent sounds are various chords.
Mark Lentczner created the software that plays the arpeggiated chord in the Macintosh II. Variations of this sound were deployed until Jim Reekes created the startup chime in the Quadra 700 through the Quadra 800. Reekes said, "The startup sound was done in my home studio on a Korg Wavestation EX. It's a C major chord, played with both hands stretched out as wide as possible (with 3rd at the top, if I recall)." He created the sound as he was annoyed with the tri-tone startup chimes because they were too associated with the death chimes and the computer crashes. He recalls that Apple did not give him permission to change the sound but that he secretly snuck the sound into the computers with the help of engineers who were in charge of the ROM chips. When Apple discovered this, he refused to change it, using various claims in order to keep the new sound intact. He is also the creator of the iconic (or "earconic", as he calls it) "bong" startup chime in most Macintoshes since the Quadra 840AV. A slightly lower-pitched version of this chime is in all PCI-based Power Macs until the iMac G3. The Macintosh LC, LC II, and Macintosh Classic II do not use the Reekes chime, instead using an F major chord that just produces a "ding" sound. The first generation of Power Macintosh computers also do not use the Reekes chime, instead using a chord strummed on a Yamaha 12-string acoustic guitar by jazz guitarist Stanley Jordan. Further, the Power Macintosh 5200–6300 computers (excluding the 5400 and 5500, which have the "bong" chime like the one in the PCI-based Power Macs) use a unique chime, which is also in the television commercials for the Power Macintosh and PowerBook series from 1995 until 1998, and the 20th Anniversary Macintosh uses another unique sound.