Q. Can a Baal Tokea blow shofar to train and prepare on the night of Rosh Hashana or on the morning before davening, if he has then specific intention of not being yotze with the mitzva?
A. See questions 858, 859 and 867, on the permissibility of blowing shofar at night during Elul; were we wrote: Horav Shlomo Miller’s Shlit”a opinion is that one may blow at night the shofar for learning purposes.
However, the Rov rules that on Yom Tov itself, one should not blow when it is not for the purpose of the mitzva as is mentioned by Poskim, including in the morning before davening.
The Rov suggested that if the baal tokea feels he needs more preparation and training, he should do so in privacy before mincha on Erev Yom Tov, or in the morning of Rosh Hashana, while visiting one unable to come to shul, with the intention of being motze him, without being yotze himself.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a