Orchestra groupies might have noticed a few interesting changes in the composition of the Philadelphia Orchestra for Thursday night's Elektra in Verizon Hall. In addition to the Wagner tubas, the orchestra was joined by a special guest playing assistant principal horn: Julie Landsman, principal horn of the Metropolitan Opera orchestra from 1985-2010. Landsman was helping out her former student, principal hornist Jennifer Montone, on the heavy-duty part.

Strauss' score calls for heckelphone, a four-foot oboe. Jonathan Blumenfeld handled the part on bass oboe. Both instruments are pitched an octave below the regular oboe.

Also, if you think you saw violists playing violin, you're right. Six violists switched to violin in the piece.

A total of 117 instrumentalists were on stage, an orchestra spokeswoman said. Not Mahler Symphony No. 8, but impressive nonetheless.

The orchestra has never done Elektra before (except for an excerpt, in 1956). So Saturday's repeat may be your last chance locally for a while.