The images below are harmonic spectrum analyses of various instruments and of gongs played with different mallets and friction mallets. The analysis illustrates how a different cluster of harmonics emerges out of the spectrum of the instrument based on how it is being played. Naturally, when I use a Paiste M1 mallet to hit the gong it is going to sound slightly different than an M6 mallet would. Every horizontal line is a harmonic, and the lower ones are the lowest harmonics and the higher ones are the highest. The thicker the line is the louder the harmonic.
The software I used is Izotope RX 3 Advanced.