Michael,
Thanks for taking the time to listen and send me feedback.
I’ve also noticed a preference among music libraries for uptempo cues. They tend to catch the listener’s attention more quickly than downtempo cues and don’t demand as much prolonged concentration. I certainly don’t mean to say that writing uptempo instrumentals is easier than writing slower pieces. In fact, I incline towards writing slow to midtempo reflective pieces and find it quite difficult to play faster musical compositions.
As for the hissing sound in the first third of Heartbeats, I intentionally placed that pseudo-gramophone sound effect there. It fades out as the central part of the cue begins. My wife didn’t care for that sound effect; she found it distracting.
Thanks again for your reply.