By "Reformed", it is clear you mean "Zwinglian" and not "Calvinist," in that Calvin proposed a spiritual presence whereas Zwingli took a sign-based approach, which was still closer to the idea of Real Change than Melancthon.
That wasn't my intent. Westminster says:
The outward elements in this sacrament, duly set apart to the uses ordained by Christ, have such relation to Him crucified, as that, truly, yet sacramentally only, they are sometimes called by the name of the things they represent, to wit, the body and blood of Christ;[10] albeit, in substance and nature, they still remain truly and only bread and wine, as they were before.[11]
...
Worthy receivers, outwardly partaking of the visible elements, in this sacrament,[13] do then also, inwardly by faith, really and indeed, yet not carnally and corporally but spiritually, receive and feed upon, Christ crucified, and all benefits of His death: the body and blood of Christ being then, not corporally or carnally, in, with, or under the bread and wine; yet, as really, but spiritually, present to the faith of believers in that ordinance, as the elements themselves are to their outward senses.[14]
The concept here is that Christ's body and blood are really, though spiritually present. The elements remain bread and wine. I think it's reasonable to refer to them as signs of Christ's body and blood, which are present with them. (I'm OK with the Lutheran in, with and under.)
I think this is consistent with Calvin. His French Confession refers to the elements as signs:
Thus we hold water, being a feeble element, still testifies to us in truth the inward cleansing of our souls in the blood of Jesus Christ by the efficacy of his Spirit, and that the
bread and wine given to us in the sacrament serve to our spiritual nourishment, inasmuch as they show, as to our sight, that the body of Christ is our meat, and his blood our drink. And we reject the Enthusiasts and Sacramentarians who will not receive such signs and marks, although our Savior said: 'This is my body, and this cup is my blood.'