Although Sylvain said Rundgren was not an interfering producer, he occasionally involved himself to improve a take. Sylvain recalled moments when Rundgren went into the isolation booth with Nolan when he struggled keeping a beat and drummed out beats on a cowbell for him to use as a click track. During another session, he stopped a take and walked out of the control room to plug in Kane's bass cabinet. Scoppa, who paid afternoon visits to the studio, overheard Rundgren say, "Yeah, that's all you needed. Okay, let's try it again!", and ultimately found the exchange funny and indicative of Rundgren's opinion of the band: "Todd was such a 'musician' while they were just getting by on attitude and energy. But as disdainful as he appeared to be at some points he got the job done really well." Rundgren felt Johansen's wild singing often sounded screamed or drunken but were eloquent in the sense that Johansen demonstrated a "propensity to incorporate certain cultural references into the music", particularly on "Personality Crisis". While recording the song, Johansen walked back into the control room and asked Rundgren if his vocals sounded "ludicrous enough".Because the New York Dolls had little money, Sylvain and Thunders played the austerely designed and affordable Gibson Les Paul Junior guitars on the record. They jokingly referred to them as "automatic guitars" due to their limited sound shaping features. To amplify their guitars, they ran a Marshall Plexi standalone amplifier through the speaker cabinets of a Fender Dual Showman, and occasionally used a Fender Twin Reverb. Some songs were embellished with additional instruments, including Buddy Bowser's brassy saxophone on "Lonely Planet Boy". Johansen sang into distorted guitar pickups for additional vocals and overdubbed them into the song. He also played an Asian gong for "Vietnamese Baby" and harmonica on "Pills". For "Personality Crisis", Sylvain originally played on The Record Plant's Yamaha grand piano before Rundgren added his own piano flourishes to both that song and "Private World". Rundgren also contributed to the background vocals heard on "Trash" and played synthesizers on "Vietnamese Baby" and "Frankenstein (Orig.)", which Sylvain recalled: "I remember him getting those weird sounds from this beautiful old Moog synthesizer he brought in. He said it was a model that only he and The Beatles had."New York Dolls was mixed in less than half a day. Rundgren felt the band seemed distracted and disinterested at that point, so he tried unsuccessfully to ban them from the mixing session. For the final mix, he minimized the sound of Nolan's drumming. In retrospect, Rundgren said the quality of the mix was poor because the band had hurried and questioned him while mixing the record: "It's too easy for it to become a free-for-all, with every musician only hearing their own part and not the whole. They all had other places to be, so rather than split, they rushed the thing and if that wasn't enough they took it to the crappy mastering lab that Mercury had put them in." Thunders famously complained to a journalist that Rundgren "fucked up the mix" on New York Dolls, adding to stories that the two had clashed during the album's recording. Both Johansen and Scoppa later said they did not see any conflict between the two and that Thunders' typically foolish behavior was misinterpreted. Johansen later praised Rundgren for how he enhanced and equalized each instrument, giving listeners the impression that "[they're] in a room and there's a band playing", while Sylvain said his mix accurately captured how the band sounded live.

Question: Who brought in a Moog Synthesizer?
Answer: Rundgren