Generate a sawtooth wave
Download a WAV file holding a 1 kHz sawtooth at -6 dBFS. The sawtooth carries the densest spectrum of the four basic shapes, which is why it is the signal filters are usually demonstrated on.
Every harmonic, falling as 1/n
A sawtooth contains the fundamental and every harmonic above it, odd and even, each at 1/n amplitude. A 1 kHz saw has energy at 2 kHz at half the level, 3 kHz at a third, 4 kHz at a quarter, and on upward until the band runs out.
A square holds the same 1/n slope but skips every even harmonic, so a sawtooth has roughly twice the spectral density at the same fundamental.
Subtractive synthesis
Removing content only works when the content is there to begin with. Sweeping a low-pass filter down a sawtooth moves through a continuous series of harmonics and produces the smooth timbral change the technique is built on. The same sweep on a triangle runs out of harmonics almost immediately.
Band limits
The series is cut off at the Nyquist frequency, 24 kHz at a 48 kHz sample rate. A truncated series overshoots at each reset of the ramp, so the sharp vertical edge shows ripple on a scope. That is the band limit, not an error in the file.
Level
The level is peak. A sawtooth’s RMS sits about 4.8 dB below its peak, so at -6 dBFS peak it measures around -10.8 dBFS RMS, quieter than a square at the same setting.
Other shapes
The square gives odd harmonics only, the triangle a far gentler series, and the sine none at all. To set frequency, level, or duration yourself, use the full Tone Generator.