I used to get the song organized "on paper", sequence the bass and drums sounds (along with piano, string sounds, etc.), mix them as best as I could on the keyboard (anticipating the latter addition of guitar and vocals), then record this "foundation" music for the song (that might contain 6 or more instrument sounds from the keyboard) onto the first track of my 4-track cassette recorder (my keyboard had L and R outputs with one of the outputs being designated for "mono", I used the mono output and connected to the 4-track as mentioned from the other posters). So I had a lot of instrument parts going on track 1 but the sounds couldn't be panned independently of one another (and I usually kept the keyboard track panned up the middle), still it was a major leap at the time in giving me posibilities that I never had before. The other 3 tracks were used for some combination of lead vocal, rhythm guitar, lead guitar, and back-up vocal (I discovered that I could often put lead guitar and back-up vocal on the same track since they often occured at different times in the song, it just required some on-the-fly (mostly volume adjustment) moves during mix-down to make everything sound right.