Ok, so what if you have studio time, but no song ideas yet? I think of that as an opportunity for lightning to strike, and keep an open mind. I start this type of session similarly to a session that is being built around an already started song - it's all about a good drum beat. I find something exciting, with no limitations on making sure it works with an existing guitar rhythm, and go from there. As I mentioned in the previous blog, I like using drum loops at this point, my favorite being Yurt Rock loops. I'll find a couple great loops, duplicate them a few times and use them to form a verse / chorus structure, adding a loop with fills before the transition if possible (this really helps me remember a change is coming as I go along).
I'll play that back over the studio monitors in loop mode (so it repeats the whole song over and over), grab an instrument and see if I can come up with something cool. Once it sounds pretty good, I record it and then move on to the vocal. I'm really looking for melody and rhythm here, but you need words too so I'm also singing words, though they don't always make sense or go together. Occasionally one of these lyrics will be golden, and a theme pops out that I can focus on and build from. Sometimes, not so much. Either way, I record this practice so I can listen later after stepping away from the process.
Often the improv session doesn't yield a usable song, but it's always a valuable experience for me. The more you build songs, the better you become at it. The only danger here is that with such a cool beat and fleshed out music, the improv lyrics can be tempting to keep. I have learned to step back and ask myself if the lyrics are meaningful or adding to the theme of the song. If not, I'll mute them and try something else. One technique I like to use is saving a mix without vocals on my phone, blasting that in the car while driving on the freeway and singing along. Sometimes I'll do that for a whole album, to get practice singing the parts and tweaking lyrics before I do final recordings.