I have a (hopefully) quick question:
I don’t recall Yogananda ji recommending any specific Hindu mantras in his books, but I do remember reading something about how he was sometimes heard reciting the Gayatri mantra. Do we know if he used the long or short form? Which form is more "authentic" from a Vedic standpoint?
It is possible that Paramhansa Yogananda chanted the Gayatri Mantra at times, though I’ve never heard any stories in that regard. He certainly must have been raised hearing and chanting that very sacred mantra while he was growning up in India. There are no records of him actually teaching the Gayatri Mantra.
There are a few mantras that he specifically did teach, most relating to various meditation techniques. One of them is the mantra "hong-sau", which is used with the technique by the same name. He also taught the use of "Aum" as a mantra, again in conjunction with a meditation technique. There is another mantra that he taught as part of one of the higher Kriya techniques.
Also, many disciples of Yogananda mentally chant the mantra "Aum Guru" throughout the day, as a way of attuning themselves with the Guru. I believe this practice was suggested by Yogananda.
Because we now live in an age of energy, called Dwapara Yuga, techniques that work directly with the life force are more effective than only mantra repetition. This is why Yogananda taught Kriya Yoga as the quickest and most powerful way to change one’s consciousness.
The Gayatri Mantra has been chanted throughout India for millennia. It has its origin in the Rig Veda, so it is perhaps the most ancient mantra of all. We chant it, along with the Mahamrityunjaya Mantra, every Sunday before our Ananda Sunday Service.
There is a beautiful recording of Swami Kriyananda chanting the Gayatri Mantra that you can order here. That version has the 'seal of approval' of some pundits in India who listened to Kriyananda chant the Gayatri.
It’s also the "form" that is most widely chanted in India, and is done just as the Vedas describe it, so it is certainly "authentic" from the Vedic viewpoint. I believe it is the "short form" you are referring to. Undoubtedly Yogananda would have used this form of the Gayatri Mantra.
I understand that there is a "long form" that is done, but I can’t speak for its authenticity, since it doesn’t seem as widely used in India. But surely more important than which form one uses is the devotion and concentration with which the mantra is chanted.