A Bass Song is a piece of music that contains low frequency notes, which is called bass. Bass notes can be acoustic, but within the term "bass song" they are usually synthesized, typically sine waves or very similar. Most of the time the term "bass song" alludes to a hip hop or rap song, but there are also reggae, techno, dubstep and other electronic songs that fall under this category.
A bass song is different from a bass test. A bass test is a recording where bass is the main point of the track, whereas in a bass song, the bass is still very prominent, yet remains supplemental to the rest of the song.
Many bass songs utilize sub-bass frequencies ranging from 25 Hz to 80 Hz, which is the general operating range for a car subwoofer setup. Ported subwoofer enclosure tuning frequencies are usually within this range.
A low frequency bassline in a bass song is usually created using a synthesizer to generate sine wave based tones, which sometimes has an acoustic or electronic kick drum sample layered on top of the attack transient. A baseline can also be created by pitch shifting an existing instrument sample, or using an acoustic bass instrument, and optionally applying a low-pass filter and/or equalization.