What a tone generator is for, beyond music
Speaker calibration, tuning reference, and why different waveforms exist.
Beyond music
A tone generator produces an exact, stable frequency — something neither singing nor playing an instrument can guarantee with the same precision. That's why it's used in fairly different contexts: equipment calibration, hearing checks, and tuning reference.
Concrete uses
Testing whether a speaker or headphone reproduces a certain frequency range well (for example, sweeping from 60 Hz to 12,000 Hz and noting where the sound weakens). Generating a fixed 440 Hz A as a tuning reference for an acoustic instrument without using the microphone. Running a simple hearing-perception check across frequencies — though a real hearing diagnosis needs a professional, not this or any online tool.
Why there are different waveforms
A sine wave is a "pure" tone, with no harmonics — the most common choice for technical tests. Square, triangle and sawtooth waves add harmonics in different patterns, and are used more for audio hardware tests that aim to stress the system with frequency-richer content.