Artistic experimentation, such as the placement of random gibberish in the run-out groove, became one of the album's defining features. "Sgt. Pepper" was the first pop album to be mastered without the momentary gaps that are typically placed between tracks as a point of demarcation. It made use of two crossfades that blended songs together, giving the impression of a continuous live performance. Although both stereo and monaural mixes of the album were prepared, the Beatles were minimally involved in what they regarded as the less important stereo mix sessions, leaving the task to Martin and Emerick. Emerick recalls: "We spent three weeks on the mono mixes and maybe three days on the stereo." Most listeners ultimately only heard the stereo version. He estimates that the group spent 700 hours on the LP, more than 30 times that of the first Beatles album, "Please Please Me", which cost £400 to produce. The final cost of "Sgt. Pepper" was approximately £25,000 ().