Sospiro Strings: Kontakt Library of Slow Swells and Sustains by Ben Osterhouse

The vibrato swells are described as warm and individual. The non-vibrato swells have a clear tone that makes the change in timbre as each instrument gets louder and softer easier to hear. Vibrato swells can sound better or worse depending on how much they are time-stretched, so the non-vibrato option is useful when you need a cleaner result.

The library includes three sustain types. Cold sustains use a slow bow with no vibrato for a fragile sound. Warm sustains are played over the fingerboard with a fast, freely changing bow and generous vibrato. Full sustains are played closer to the bridge with a slow, heavy bow, with vibrato used sparingly.

The Length in Beats slider selects the swell that matches your chosen length, time-stretching it when needed. The Length Multiplier helps when a project's tempo is fast but you want a slow sound, or the reverse.

Smart Release makes the release longer the longer you hold a note, based on how far into the crescendo you have held it. Sync sets any notes you add or change in a chord to match the first note played. A doubling option layers two instances with slight stereo spread, which suits a single instrument playing a few notes; with large chords across all four instruments it tends to sound more generic, according to the developer.