A common definition of tenuto that is bandied about is hold for the full value of the note. This definition is half right in that one note is connected to the following note, so still articulated but without a gap.
The one thing however, that is often missing from this definition is the gentle weight that is given to the beginning of each tenuto note. It’s a bit like walking along carrying heavy bags and each step requires a bit of effort to keep the momentum going.
In previous blogs, I’ve written about the tongue being just behind the front teeth on the alveolar ridge. For tenuto however; the tongue tends to move back, away from the teeth, along the ridge as if saying the sounds do or da. It is a gentler and somewhat rounded tongue action.
Using this tongue action with a gentle detaché pulse can give the tenuto note the weight it requires at the beginning. You can even try dropping your chin slightly for each note to darken the sound a little if that is appropriate for the music you are playing.
So if your standard idea for tenuto is hold for its full value, try adding that smidge of weight at the beginning of each note to create more interest in your articulation.