This paper proposes a working definiton of everyday musical creativity and describes the results of an experimental study involving six musicians and non-musicians. Subjects participated in 47 mixing sessions using samples collected at two outdoors sites - one featuring urban sounds and the other highlighting animal sounds - and in studio settings. Creativity support was evaluated by means of the CSI-NAP protocol. Outdoor sessions yielded higher scores in productivity, explorability, concentration and colaboration when compared to studio sessions. Compound effects of sound sample type and activity location were observed in the explorability factor when animal sounds were used. Similar effects were detected on explorability, productivity and concentration when urban sounds were employed. We put forth two theoretical hypotheses to explain these findings, incorporating engagement and cognitive effort constructs within everyday creative phenomena.