Rundgren played a large role in the album's sound design and drum programming, providing the band with string and brass arrangements, as well as an assortment of gear that included a Fairlight CMI, Yamaha DX7, E-mu Emulator, pre-MIDI LinnDrum, and a Prophet-10 bought especially for the album. The only instruments the band had brought with them to the US were "about eight guitars". Gregory repaired a neglected Chamberlin that had become infested with mice. They spent the first week planning and setting markers for the tape space they needed. Another three weeks were spent programming percussion and other sequences on a Fairlight. For the first run of sessions at Woodstock, the group used the LinnDrum as a placeholder for percussion, which Gregory said "sounded very stiff and lifeless". Real drums were overdubbed at Sound Hole Studios in San Francisco by the Tubes' Prairie Prince. Gregory said "it was only then that the album started coming to life".