Yes, it is possible to combine frequency modulation (FM) and amplitude modulation (AM) in the same signal. This technique is known as amplitude and frequency modulation (AFM) or simply as amplitude and frequency modulation.
In AFM, both the frequency and the amplitude of the carrier signal are simultaneously modulated by two different input signals. This can be achieved by first applying an amplitude modulation to the carrier signal, resulting in a signal with varying amplitude. Then, this modulated signal can be further modulated with frequency modulation, causing the carrier frequency to vary in accordance with the second input signal.
The resulting AFM signal contains variations in both frequency and amplitude. This technique can be used in various applications, including telecommunications, radio broadcasting, and audio synthesis. However, it's worth noting that AFM is less commonly used compared to individual FM or AM modulation techniques, as it can introduce more complexity and potential for interference in the signal.