Single tone M-ary frequency shift keying (MFSK) enjoys constant envelop transmission at the expense of much lower spectral efficiency (SE). Many research efforts were given for enhancing the SE of MFSK. In this paper, SE of coherent single tone MFSK is improved by filling up the same allocated spectral band-width by larger number of uniformly spaced non-orthogonal tones. The main idea resides in two main points, first, regarding the detection task as an operation of super-resolution (SR) spectral line estimation, second, highlighting implicit sparsity construction of MFSK scheme. Compressive sensing (CS) based SR approaches are enabled for resolving activated atom from over-complete dictionary. Moreover, more general keying schemes can be performed on learned dictionary instead of the classical Fourier (sinusoidal) dictionary, where each atom may occupy the whole allocated spectrum instead of …