For a little variety, you can use the 60 minute Delta Ultra Deep Standalone Meditation which takes you down into Delta and holds you there for an extended period of time. If you can stay awake during this entire time, you will have some amazing meditative experiences. (If you fall asleep, don't worry! It's natural and with practice you will be able to stay awake more often.)

The phenomena of brainwave entrainment was first described in the scientific literature in 1973 by Gerald Oster in results published in an article in Scientific American entitled, “Auditory Beats in the Brain”. He showed that a specific brainwave could be induced when a person heard two separate, but closely related, sound frequencies, one in each ear. He discovered that when the frequencies heard by each ear differed by about 10 hertz, the brainwave pattern of the person hearing the sound would synchronize to the difference between the two frequencies. For example, if the person heard a 410 hertz sound in one ear and a 400 hertz sound in the other ear, their brainwaves would stabilize at the difference between the two, or 10 hertz. This technique is called binaural beats, and it is a fundamental principle of brainwave entrainment methods.
^ Trost W. and Vuilleumier P., Rhythmic entrainment as a mechanism for emotion induction by music: a neurophysiological perspective. In The Emotional Power of Music: Multidisciplinary Perspectives on Musical Arousal, Expression, and Social Control, Cochrane T., Fantini B., and Scherer K. R., (Eds.), Oxford, UK: Oxford University Press; 2013, pp213–225.

OK – so some of this is pretty common marketing hype. Consumers have become almost numb to such hyperbole. But still we see some of the common – almost ubiquitous – elements of pseudoscientific scams. The company claims that the device is “effort-free”, that the results are “rapid and long-lasting,” that it is the “most effective” method of its kind, and that it is useful for a broad range of applications (hey, why limit the market). I am used to such hype about dishwashing detergent, but find it intolerable when applied to a pseudoscientific device with medical applications.
It should be stated that if we are listening to LifeFlow and we are intentionally seeking to enter into meditation, the chances are good that we will do exactly that rather than just being in a daydream or some other pleasant state. It’s no guarantee, but the combination of meditation and brainwave entrainment raises the odds that we will accomplish our meditative goal.
... Audio visual stimulation effects people on two levels: Budzynski (2001) reports significant improvement of mental capabilities after AVS in 75-year old male. Cruceanu and Rotarescu (2013) proved that the exposure to 30-minutes of audio-visual stimulation with the frequency of 10,2 Hz significantly improves cognitive skills. Based on their research, authors claim that people need to be exposed to AVS at least for 20 minutes in order to achieve positive effects. ...
However, yoga and meditation take time to learn and master, and until the student becomes proficient, progress can be slow and frustrating, leading many people to abandon the effort before they see the benefits. Brainwave entrainment has the potential for helping a person enter the relaxing and rejuvenating mind-states brought about by yoga and meditation without the learning curve and time needed for mastering these other techniques. Brainwave entrainment may even facilitate learning other mindfulness methods by helping a person achieve success faster and more reliably. 
Gamma waves are the fastest of the brainwave frequencies (high frequency band of brainwave activity) which signifies the highest state of focus possible. They are associated with peak concentration and the brain’s optimal frequency for cognitive functioning – the 40 Hz frequency corresponds to a Schumann resonance band and many scientists, including Nobel Laureate Sir Francis Crick believe that it may be the key to the act of cognition. The Gamma state relates to simultaneous processing of information from different brain areas; information passes very rapidly.

Beginning with greater influence on our health, our connection with the universe will lead to enhanced insight and creativity and our ability to influence the evolution of reality, clearing a pathway towards harmony and peace in our lives and in the world-at-large. Using Sacred Acoustics recordings and other methods, we can discover an inner stillness deep enough to connect with our divine spiritual nature. With Living in a Mindful Universe, we show readers how to achieve this same access to the Collective Mind.
Brain Wave Entrainment is any procedure that causes one's brainwave frequencies to synchronize with a periodic stimulus (sound, vibration or light) having a frequency corresponding to the intended brain-state (for example, to induce a trance, dreams, sleep or relaxation.) It is also called the Flicker-response because of how staring at a campfire or the flickering of a burning candle can lull you into a state of calmness and serenity. There was an extensive article on this phenomenon by Gerard Oster in Scientific American in 1973. It may sound novel, but in many ways, this is old tech.
Brainwave entrainment is a colloquialism for such 'neural entrainment', which is a term used to denote the way in which the aggregate frequency of oscillations produced by the synchronous electrical activity in ensembles of cortical neurons can adjust to synchronize with the periodic vibration of an external stimuli, such as a sustained acoustic frequency perceived as pitch, a regularly repeating pattern of intermittent sounds, perceived as rhythm, or of a regularly rhythmically intermittent flashing light.