Best method for transposing for maximal learning
I don't want to overcomplicate this question and it is probably not that deep but, I am learning this tune where the lead sheet is in D Major. I have done the harmonic function analysis and written the roman numerals above each chord. I have not learned the tune yet. I want to learn it in G because I want to sing over it and it fits my range better.
Should I keep the marked up lead sheet in D and mentally transpose everything to G while learning the tune? Or should I just handwrite my own lead sheet on G on a staff of paper?
Obviously the second option would be the least hassle for me and the easiest way to learn it in G but I don't want to be "cheating" and miss out on the benefits of transposing mentally if there are any.
The same question could be formulated for learning a tune in 12 keys after knowing it by heart in one key. Do you guys transpose it mentally at your instrument or do you create a new lead sheet with the transposed changes and melody?