Rhythms　of　the　brain　are　generated　by　neural　oscillations　across　multiple　frequencies.　These　oscillations　can　be　decomposed　into　distinct　frequency　intervals　associated　with　specific　physiological　processes.　In　practice,　the　number　and　ranges　of　decodable　frequency　intervals　are　determined　by　sampling　parameters,　often　ignored　by　researchers.　To　improve　the　situation,　we　report　on　an　open　toolbox　with　a　graphical　user　interface　for　decoding　rhythms　of　the　brain　system　(DREAM).　We　provide　worked　examples　of　DREAM　to　investigate　frequency-specific　performance　of　both　neural　(spontaneous　brain　activity)　and　neurobehavioral　(in-scanner　head　motion)　oscillations.　DREAM　decoded　the　head　motion　oscillations　and　uncovered　that　younger　children　moved　their　heads　more　than　older　children　across　all　five　frequency　intervals　whereas　boys　moved　more　than　girls　in　the　age　of　7　to　9　years.　It　is　interesting　that　the　higher　frequency　bands　contain　more　head　movements,　and　showed　stronger　age-motion　associations　but　weaker　sex-motion　interactions.　Using　data　from　the　Human　Connectome　Project,　DREAM　mapped　the　amplitude　of　these　neural　oscillations　into　multiple　frequency　bands　and　evaluated　their　test-retest　reliability.　The　resting-state　brain　ranks　its　spontaneous　oscillation＇s　amplitudes　spatially　from　high　in　ventral-temporal　areas　to　low　in　ventral-occipital　areas　when　the　frequency　band　increased　from　low　to　high,　while　those　in　part　of　parietal　and　ventral　frontal　regions　are　reversed.　The　higher　frequency　bands　exhibited　more　reliable　amplitude　measurements,　implying　more　inter-individual　variability　of　the　amplitudes　for　the　higher　frequency　bands.　In　summary,　DREAM　adds　a　reliable　and　valid　tool　to　mapping　human　brain　function　from　a　multiple-frequency　window　into　brain　waves.