This game is pretty much well known and plus its really easy to understand and play so heres how it works:
We start out with the letter 'A,' post a word that begins with that letter,
the next person can either choose to go onto the consecutive letters (ex. B, C, D etc.) or they could take the last letter of the previous word and continue on from there.
Ex.
Person1: Acappella
Person2: Bass
or Ex.
Person1: Alto-Calrinet
Person2: Tenor
etc.
The theme for this is anything that has to do with music, like chorus, band, music bands, singers etc.