In the investigation of musical features that influence musical affect, timbre has received relatively little attention. Investigating affective timbres as they vary between instrument families can lead to inconsistent results, because one instrument family can produce a wide variety of timbres. Here, we consider timbre descriptors, as fine-grained acoustic representations of a sound. Using identical methods, we re-analyzed and synthesized results from three previously published studies: Eerola et al. (2012, Mus. Percept.), McAdams et al. (2017, Front. Psychol.), and Korsmit et al. (2023, Front. Psychol.). In doing so, we aimed to reveal robust timbre descriptors that consistently predict the affective response and to explain any discrepancies in results arising from differences in experimental methodology. We computed spectral, temporal, and spectro-temporal descriptors from all stimuli and used these to predict the affect ratings using linear and nonlinear methods. Our most consistent finding was that the fundamental frequency or higher-frequency energy of a sound predicted pleasant affect (i.e., positive valence, happiness, sadness) in one direction and unpleasant affect (i.e., tension, anger, fear) in the opposite direction. Clear discrepancies in previous findings may be attributable to differences in experimental design. When pitch variation was present in a stimulus set, energy arousal was predicted by pitch and inharmonicity, whereas when attack variation was present in the stimulus set, energy arousal was predicted by a faster attack and shorter sustain.