Yes, Rob Rokicki's score to ''The Lightning Thief'' was the only eligible score from a musical in this COVID-shortened Broadway season.
Had it not been for the virus, I imagine it might've competed for Best Score, alongside ''Flying Over Sunset,'' ''Mrs. Doubtfire'' and ''Six.''
I still think ''The Lightning Thief'' got a raw deal. I enjoyed a number of its tunes, like ''Bring on the Monsters'' and ''Good Kid.'' It was worthy of a nomination, especially compared to a number of Tony-nominated scores I could name. ''Merlin,'' anyone? ''Metro''? ''Copperfield''? ''The News''?
I also believe Chris McCarrell and Ryan Knowles gave award-caliber performances in ''The Lightning Thief'' that deserved Tony recognition.
By the way, since 1980, the Drama Desks have given out a separate award for Music of a Play (in addition to Lyrics and Music of a Musical).