Spectrum of FM signal?
With a more complex modulation signal, the forest of sidebands gets denser, but the overall envelope stays much the same as you have illustrated. For low modulation index, the envelope looks like a broadened line with a peak at the centre frequency. For high modulation index, there are a low and high frequency lowish peak (representing the time the carrier spends dwelling at the extreme of either frequency shift), with a broad lower plateau between (as it zips quickly between the two extremes).