Amplitude factor for the harmonic (ℓ,m) of the gravitational wave emitted by an orbiting point mass (cf. Eq. (6)), in terms of the orbital radius r₀. Each panel corresponds to a given value of the MBH spin: a = 0 (Schwarzschild BH), a = 0.5 M, a = 0.9 M and a = 0.98 M. A given color corresponds to a fixed value of ℓ and the line style indicates the value of m: solid: m = ℓ, dashed: m = ℓ − 1, dot-dashed: m = ℓ − 2, dotted: 0 <  m ⩽ ℓ − 3.