People hold of the restrictions of the seven-week omer period (shaving and listening to music, for example) at various times: some hold approximately the first five weeks; others, approximately the last five weeks. I heard in a shiur that Rav Moshe Feinstein holds that one can hold by both periods of the omer for different prohibitions. One half for shaving and the other for music. Where can it be found in his teshuvos?
In Igros Moshe Orach Chaim 1 - Siman 159 HaRav Moshe Feinstein Zatzal talks about whether there is a problem with Tarte De'Sasre if someone gets married during a time in Sefira that others keep the Sefira restrictions. However there is no mention of keeping different parts of Sefira for shaving and another for music.