A broad-band proton-decoupled proton NMR spectrum, in which all of the proton multiplets collapse to sharp singlets, has been pursued since the early days of NMR. Two-dimensional (2D) methods, like a skew 45 projection of an absolute-value (AV) J-spectrum¹ or a constant-time (CT) experiment^2,3 are hampered by poor resolution because of phase-twist line shapes. Furthermore, high resolution is required in the F₁ dimension, lengthening experiment time and reducing sensitivity.⁴ The J-spectrum has thus fallen into disuse; the 45 projection is unimpressive, and the 2D spectrum is of only marginal help for assignment. Heavy digital filtering by a "pseudo-echo"⁵ improves AV line shapes but introduces intensity distortions and sensitivity loss. Frequency-domain fitting routines⁶ require a high-resolution data matrix of lines with similar widths and do not necessarily converge.