Selective Spin-Locking (SSL) of the magnetisation vectors of selected singlets or multiplets in high-resolution Nuclear Magnetic Resonance (NMR) spectra by mono- or polychromatic selective radio-frequency (RF) irradiation can reduce the line-widths to the limit given by homogeneous <em>T</em><sub>1</sub><sub>ρ</sub> relaxation. The resulting line-narrowing leads to an increase in signal height of spectra of <sup>1</sup>H, <sup>19</sup>F, <sup>31</sup>P or other nuclei that is in principle only limited by the ratio <em>T</em><sub>1</sub><sub>ρ</sub>/<em>T</em><sub>2</sub>*. At the same time, the scalar interactions that give rise to multiplets are decoupled, thus leading to an additional gain in signal height. Common one-dimensional (1D) experiments such as inversion recovery (IR) as well as the excitation and reconversion of Long-Lived States (LLS) by Spin-Lock Induced Crossing (SLIC) can significantly benefit from SSL.