I have a level 10 bard, who is looking to make some assassinations during the course of the campaign. Dissonant whispers has the nice property of only the target hearing the whisper itself.
However, it has a range of paltry 60 feet, which is uncomfortably close in many situations, especially if DM makes a harsh ruling about the audibility of the verbal components of the spell (even if the actual whisper is inaudible).
Is there a way to increase the range of Dissonant Whispers?
Multiclassing Bard/X is possible but not preferable. Other options I can think of are magic items and feats.
Preferred sources are the core books and Xanathar's Guide to Everything. Setting is Exandria, so at least the Tal Dorei and Wildemount books would be acceptable too.
If the method applies to other verbal-only saving throw spells of the Bard, all the better of course.
Note: The Spell Sniper feat does not apply, as it requires a spell with an attack roll.